public class GCD {

public static void main (String[] args) {
  if (args.length != 2) System.err.println("Usage: GCD integer1 integer2");
  else System.out.println(
    "The greatest common divisor of " + args[0] + " and " + args[1] + " is " 
    + gcd(Integer.parseInt(args[0]), Integer.parseInt(args[1])));
}

static int gcd (int a, int b) 
{ 
  System.out.println("a= " + a + " b= " + b);
  if (b < a) return gcd(b, a);
  if (b % a == 0) return a; 
  else return gcd(b, b % a); 
}

}