/******************************************************************************
 *  Compilation:  javac Damier.java 
 *  Execution:    java Damier N
 *  Dependences:  StdDraw.java
 *
 *  Trace un damier NxN .
 *
 ******************************************************************************/

public class Damier { 

    public static void main(String[] args) { 
        int N = Integer.parseInt(args[0]);
        StdDraw.setXscale(-0.5, N-0.5);
        StdDraw.setYscale(-0.5, N-0.5);

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                if ((i + j) % 2 != 0) 
					StdDraw.setPenColor(StdDraw.BLACK);
                else                  
					StdDraw.setPenColor(StdDraw.RED);
                StdDraw.filledSquare(i, j, 0.5);
            }
        }
        StdDraw.show();
    }

}