Assuming 6.0 feet between all classroom chairs.

Room dimensions:  15 feet by 12 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 1 even columns of 2, total chairs = 8
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 15 by 12 is 9.

======================================================
Room dimensions:  15 feet by 13 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 1 even columns of 2, total chairs = 8
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 15 by 13 is 9.

======================================================
Room dimensions:  15 feet by 14 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 1 even columns of 2, total chairs = 8
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 15 by 14 is 9.

======================================================
Room dimensions:  15 feet by 15 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 1 even columns of 3, total chairs = 9
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 15 by 15 is 9.

======================================================
Room dimensions:  15 feet by 16 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 1 even columns of 3, total chairs = 9
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 15 by 16 is 12.

======================================================
Room dimensions:  15 feet by 17 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 1 even columns of 3, total chairs = 9
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 15 by 17 is 12.

======================================================
Room dimensions:  15 feet by 18 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 1 even columns of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 15 by 18 is 12.

======================================================
Room dimensions:  15 feet by 19 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 1 even columns of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 15 by 19 is 12.

======================================================
Room dimensions:  15 feet by 20 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 1 even columns of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 15 by 20 is 12.

======================================================
Room dimensions:  16 feet by 12 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 16 by 12 is 10.

======================================================
Room dimensions:  16 feet by 13 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 16 by 13 is 10.

======================================================
Room dimensions:  16 feet by 14 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 16 by 14 is 10.

======================================================
Room dimensions:  16 feet by 15 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 16 by 15 is 12.

======================================================
Room dimensions:  16 feet by 16 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 16 by 16 is 12.

======================================================
Room dimensions:  16 feet by 17 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 16 by 17 is 12.

======================================================
Room dimensions:  16 feet by 18 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 16 by 18 is 14.

======================================================
Room dimensions:  16 feet by 19 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 16 by 19 is 14.

======================================================
Room dimensions:  16 feet by 20 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 16 by 20 is 14.

======================================================
Room dimensions:  17 feet by 12 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 17 by 12 is 10.

======================================================
Room dimensions:  17 feet by 13 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 17 by 13 is 10.

======================================================
Room dimensions:  17 feet by 14 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 17 by 14 is 10.

======================================================
Room dimensions:  17 feet by 15 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 1 even rows of 3, total chairs = 9
* * * 
 * * *
* * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 17 by 15 is 12.

======================================================
Room dimensions:  17 feet by 16 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 17 by 16 is 12.

======================================================
Room dimensions:  17 feet by 17 feet
Arranging chairs rectangularly, 3 by 3, total chairs = 9
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 17 by 17 is 12.

======================================================
Room dimensions:  17 feet by 18 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 17 by 18 is 14.

======================================================
Room dimensions:  17 feet by 19 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 17 by 19 is 14.

======================================================
Room dimensions:  17 feet by 20 feet
Arranging chairs rectangularly, 3 by 4, total chairs = 12
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 3,
  and 2 even rows of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 17 by 20 is 14.

======================================================
Room dimensions:  18 feet by 12 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 18 by 12 is 12.

======================================================
Room dimensions:  18 feet by 13 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 18 by 13 is 12.

======================================================
Room dimensions:  18 feet by 14 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 18 by 14 is 12.

======================================================
Room dimensions:  18 feet by 15 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 18 by 15 is 12.

======================================================
Room dimensions:  18 feet by 16 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 18 by 16 is 14.

======================================================
Room dimensions:  18 feet by 17 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 18 by 17 is 14.

======================================================
Room dimensions:  18 feet by 18 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 18 by 18 is 16.

======================================================
Room dimensions:  18 feet by 19 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 18 by 19 is 16.

======================================================
Room dimensions:  18 feet by 20 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 18 by 20 is 16.

======================================================
Room dimensions:  19 feet by 12 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 19 by 12 is 12.

======================================================
Room dimensions:  19 feet by 13 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 19 by 13 is 12.

======================================================
Room dimensions:  19 feet by 14 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 19 by 14 is 12.

======================================================
Room dimensions:  19 feet by 15 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 19 by 15 is 12.

======================================================
Room dimensions:  19 feet by 16 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 19 by 16 is 14.

======================================================
Room dimensions:  19 feet by 17 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 19 by 17 is 14.

======================================================
Room dimensions:  19 feet by 18 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 19 by 18 is 16.

======================================================
Room dimensions:  19 feet by 19 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 19 by 19 is 16.

======================================================
Room dimensions:  19 feet by 20 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 19 by 20 is 16.

======================================================
Room dimensions:  20 feet by 12 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 20 by 12 is 12.

======================================================
Room dimensions:  20 feet by 13 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 20 by 13 is 12.

======================================================
Room dimensions:  20 feet by 14 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 2, total chairs = 10
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 20 by 14 is 12.

======================================================
Room dimensions:  20 feet by 15 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 3, total chairs = 11
* * * * 
 * * *
* * * * 
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 20 by 15 is 12.

======================================================
Room dimensions:  20 feet by 16 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 20 by 16 is 14.

======================================================
Room dimensions:  20 feet by 17 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 3,
  and 2 even columns of 3, total chairs = 12
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 20 by 17 is 14.

======================================================
Room dimensions:  20 feet by 18 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 20 by 18 is 16.

======================================================
Room dimensions:  20 feet by 19 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 20 by 19 is 16.

======================================================
Room dimensions:  20 feet by 20 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Filling offset columns, there are 2 odd columns of 4,
  and 2 even columns of 3, total chairs = 14
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 20 by 20 is 16.

======================================================
Room dimensions:  21 feet by 12 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 21 by 12 is 13.

======================================================
Room dimensions:  21 feet by 13 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 21 by 13 is 13.

======================================================
Room dimensions:  21 feet by 14 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 21 by 14 is 13.

======================================================
Room dimensions:  21 feet by 15 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 21 by 15 is 15.

======================================================
Room dimensions:  21 feet by 16 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 21 by 16 is 16.

======================================================
Room dimensions:  21 feet by 17 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 21 by 17 is 16.

======================================================
Room dimensions:  21 feet by 18 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 21 by 18 is 18.

======================================================
Room dimensions:  21 feet by 19 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 21 by 19 is 18.

======================================================
Room dimensions:  21 feet by 20 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 21 by 20 is 18.

======================================================
Room dimensions:  22 feet by 12 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 22 by 12 is 13.

======================================================
Room dimensions:  22 feet by 13 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 22 by 13 is 13.

======================================================
Room dimensions:  22 feet by 14 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 22 by 14 is 13.

======================================================
Room dimensions:  22 feet by 15 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 22 by 15 is 15.

======================================================
Room dimensions:  22 feet by 16 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 22 by 16 is 16.

======================================================
Room dimensions:  22 feet by 17 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 22 by 17 is 16.

======================================================
Room dimensions:  22 feet by 18 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 22 by 18 is 18.

======================================================
Room dimensions:  22 feet by 19 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 22 by 19 is 18.

======================================================
Room dimensions:  22 feet by 20 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 22 by 20 is 18.

======================================================
Room dimensions:  23 feet by 12 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 23 by 12 is 13.

======================================================
Room dimensions:  23 feet by 13 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 23 by 13 is 13.

======================================================
Room dimensions:  23 feet by 14 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 23 by 14 is 13.

======================================================
Room dimensions:  23 feet by 15 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 1 even rows of 4, total chairs = 12
* * * * 
 * * * *
* * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 23 by 15 is 15.

======================================================
Room dimensions:  23 feet by 16 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 23 by 16 is 16.

======================================================
Room dimensions:  23 feet by 17 feet
Arranging chairs rectangularly, 4 by 3, total chairs = 12
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 23 by 17 is 16.

======================================================
Room dimensions:  23 feet by 18 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 23 by 18 is 18.

======================================================
Room dimensions:  23 feet by 19 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 23 by 19 is 18.

======================================================
Room dimensions:  23 feet by 20 feet
Arranging chairs rectangularly, 4 by 4, total chairs = 16
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 4,
  and 2 even rows of 4, total chairs = 16
* * * * 
 * * * *
* * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 23 by 20 is 18.

======================================================
Room dimensions:  24 feet by 12 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 24 by 12 is 15.

======================================================
Room dimensions:  24 feet by 13 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 24 by 13 is 15.

======================================================
Room dimensions:  24 feet by 14 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 24 by 14 is 15.

======================================================
Room dimensions:  24 feet by 15 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 24 by 15 is 15.

======================================================
Room dimensions:  24 feet by 16 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 24 by 16 is 18.

======================================================
Room dimensions:  24 feet by 17 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 24 by 17 is 18.

======================================================
Room dimensions:  24 feet by 18 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 24 by 18 is 20.

======================================================
Room dimensions:  24 feet by 19 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 24 by 19 is 20.

======================================================
Room dimensions:  24 feet by 20 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 24 by 20 is 20.

======================================================
Room dimensions:  25 feet by 12 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 25 by 12 is 15.

======================================================
Room dimensions:  25 feet by 13 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 25 by 13 is 15.

======================================================
Room dimensions:  25 feet by 14 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 2, total chairs = 13
* * * 
 * *
* * * 
 * *
* * * 
Therefore, the optimal number of chairs for a room measuring 25 by 14 is 15.

======================================================
Room dimensions:  25 feet by 15 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 25 by 15 is 15.

======================================================
Room dimensions:  25 feet by 16 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 25 by 16 is 18.

======================================================
Room dimensions:  25 feet by 17 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 2 even columns of 3, total chairs = 15
* * * 
 * * *
* * * 
 * * *
* * * 
Therefore, the optimal number of chairs for a room measuring 25 by 17 is 18.

======================================================
Room dimensions:  25 feet by 18 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 25 by 18 is 20.

======================================================
Room dimensions:  25 feet by 19 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 25 by 19 is 20.

======================================================
Room dimensions:  25 feet by 20 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 2 even columns of 3, total chairs = 18
* * * * 
 * * *
* * * * 
 * * *
* * * * 
Therefore, the optimal number of chairs for a room measuring 25 by 20 is 20.

======================================================
Room dimensions:  26 feet by 12 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 26 by 12 is 15.

======================================================
Room dimensions:  26 feet by 13 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 26 by 13 is 15.

======================================================
Room dimensions:  26 feet by 14 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 26 by 14 is 15.

======================================================
Room dimensions:  26 feet by 15 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 4, total chairs = 14
* * * * * 
 * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 26 by 15 is 18.

======================================================
Room dimensions:  26 feet by 16 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 26 by 16 is 18.

======================================================
Room dimensions:  26 feet by 17 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 26 by 17 is 18.

======================================================
Room dimensions:  26 feet by 18 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 26 by 18 is 21.

======================================================
Room dimensions:  26 feet by 19 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 26 by 19 is 21.

======================================================
Room dimensions:  26 feet by 20 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 4, total chairs = 18
* * * * * 
 * * * *
* * * * * 
 * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 26 by 20 is 21.

======================================================
Room dimensions:  27 feet by 12 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 27 by 12 is 15.

======================================================
Room dimensions:  27 feet by 13 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 27 by 13 is 15.

======================================================
Room dimensions:  27 feet by 14 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 27 by 14 is 15.

======================================================
Room dimensions:  27 feet by 15 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 27 by 15 is 18.

======================================================
Room dimensions:  27 feet by 16 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 27 by 16 is 20.

======================================================
Room dimensions:  27 feet by 17 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 27 by 17 is 20.

======================================================
Room dimensions:  27 feet by 18 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 27 by 18 is 21.

======================================================
Room dimensions:  27 feet by 19 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 27 by 19 is 21.

======================================================
Room dimensions:  27 feet by 20 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 27 by 20 is 21.

======================================================
Room dimensions:  28 feet by 12 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 28 by 12 is 15.

======================================================
Room dimensions:  28 feet by 13 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 28 by 13 is 15.

======================================================
Room dimensions:  28 feet by 14 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 28 by 14 is 15.

======================================================
Room dimensions:  28 feet by 15 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 28 by 15 is 18.

======================================================
Room dimensions:  28 feet by 16 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 28 by 16 is 20.

======================================================
Room dimensions:  28 feet by 17 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 28 by 17 is 20.

======================================================
Room dimensions:  28 feet by 18 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 28 by 18 is 21.

======================================================
Room dimensions:  28 feet by 19 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 28 by 19 is 21.

======================================================
Room dimensions:  28 feet by 20 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 28 by 20 is 21.

======================================================
Room dimensions:  29 feet by 12 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 29 by 12 is 15.

======================================================
Room dimensions:  29 feet by 13 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 29 by 13 is 15.

======================================================
Room dimensions:  29 feet by 14 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 29 by 14 is 15.

======================================================
Room dimensions:  29 feet by 15 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 1 even rows of 5, total chairs = 15
* * * * * 
 * * * * *
* * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 29 by 15 is 18.

======================================================
Room dimensions:  29 feet by 16 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 29 by 16 is 20.

======================================================
Room dimensions:  29 feet by 17 feet
Arranging chairs rectangularly, 5 by 3, total chairs = 15
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 29 by 17 is 20.

======================================================
Room dimensions:  29 feet by 18 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 29 by 18 is 21.

======================================================
Room dimensions:  29 feet by 19 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 29 by 19 is 21.

======================================================
Room dimensions:  29 feet by 20 feet
Arranging chairs rectangularly, 5 by 4, total chairs = 20
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 5,
  and 2 even rows of 5, total chairs = 20
* * * * * 
 * * * * *
* * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 29 by 20 is 21.

======================================================
Room dimensions:  30 feet by 12 feet
Arranging chairs rectangularly, 6 by 3, total chairs = 18
* * * 
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 6,
  and 1 even rows of 5, total chairs = 17
* * * * * * 
 * * * * *
* * * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 30 by 12 is 18.

======================================================
Room dimensions:  30 feet by 13 feet
Arranging chairs rectangularly, 6 by 3, total chairs = 18
* * * 
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 6,
  and 1 even rows of 5, total chairs = 17
* * * * * * 
 * * * * *
* * * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 30 by 13 is 18.

======================================================
Room dimensions:  30 feet by 14 feet
Arranging chairs rectangularly, 6 by 3, total chairs = 18
* * * 
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 6,
  and 1 even rows of 5, total chairs = 17
* * * * * * 
 * * * * *
* * * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 2, total chairs = 15
* * * 
 * *
* * * 
 * *
* * * 
 * *
Therefore, the optimal number of chairs for a room measuring 30 by 14 is 18.

======================================================
Room dimensions:  30 feet by 15 feet
Arranging chairs rectangularly, 6 by 3, total chairs = 18
* * * 
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 6,
  and 1 even rows of 5, total chairs = 17
* * * * * * 
 * * * * *
* * * * * * 
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 30 by 15 is 18.

======================================================
Room dimensions:  30 feet by 16 feet
Arranging chairs rectangularly, 6 by 3, total chairs = 18
* * * 
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 6,
  and 2 even rows of 5, total chairs = 22
* * * * * * 
 * * * * *
* * * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 30 by 16 is 22.

======================================================
Room dimensions:  30 feet by 17 feet
Arranging chairs rectangularly, 6 by 3, total chairs = 18
* * * 
* * * 
* * * 
* * * 
* * * 
* * * 
Filling offset rows, there are 2 odd rows of 6,
  and 2 even rows of 5, total chairs = 22
* * * * * * 
 * * * * *
* * * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 3,
  and 3 even columns of 3, total chairs = 18
* * * 
 * * *
* * * 
 * * *
* * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 30 by 17 is 22.

======================================================
Room dimensions:  30 feet by 18 feet
Arranging chairs rectangularly, 6 by 4, total chairs = 24
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 6,
  and 2 even rows of 5, total chairs = 22
* * * * * * 
 * * * * *
* * * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 30 by 18 is 24.

======================================================
Room dimensions:  30 feet by 19 feet
Arranging chairs rectangularly, 6 by 4, total chairs = 24
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 6,
  and 2 even rows of 5, total chairs = 22
* * * * * * 
 * * * * *
* * * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 30 by 19 is 24.

======================================================
Room dimensions:  30 feet by 20 feet
Arranging chairs rectangularly, 6 by 4, total chairs = 24
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
* * * * 
Filling offset rows, there are 2 odd rows of 6,
  and 2 even rows of 5, total chairs = 22
* * * * * * 
 * * * * *
* * * * * * 
 * * * * *
Filling offset columns, there are 3 odd columns of 4,
  and 3 even columns of 3, total chairs = 21
* * * * 
 * * *
* * * * 
 * * *
* * * * 
 * * *
Therefore, the optimal number of chairs for a room measuring 30 by 20 is 24.

======================================================
In 83 of 144 cases, it is advantageous to arrange the chairs in an offset pattern.