/* Double.java
 * Practice file input and output.
 * Read an input file of numbers.  Double each number, and print
 *   corresponding results to output file.
 */
import java.util.Scanner;
import java.io.FileInputStream;		// for reading files
import java.io.FileNotFoundException;	// in case file doesn't exist!
import java.io.PrintStream;			// for file output

public class Double
{
  public static void main(String [] args) throws FileNotFoundException
  {
    // Open both files.
    Scanner inFile = new Scanner(new FileInputStream("double.in"));
    PrintStream outFile = new PrintStream("double.out");

    // Read all integers in input file.
    while(inFile.hasNextInt())
    {
      int num = inFile.nextInt();

      // Put the doubled value in the output file.
      outFile.printf("%d\n", 2 * num);
    }

    // By the way, it's generally considered good style and safe to 
    // remember to close the files used for I/O.  This will ensure that
    // all the output makes its way to the output file.
    inFile.close();
    outFile.close();
  }
}