// Exercises from Lecture 3

// greatest common divisor

using System;

public class GCD {

  public static void Main (string []args) {
     if (args.Length != 2) { // expect 2 args: x and y
       System.Console.WriteLine("Usage: exercise3d <int> <int>");
     } else {
       int x = Convert.ToInt32(args[0]);
       int y = Convert.ToInt32(args[1]);
       System.Console.WriteLine("gcd({0},{1}) = {2}", x, y, GCD.gcd(x,y));
     }
  }

  public static int gcd (int x, int y) {
	int res;
	if (x<y) {
	    res = GCD.gcd(y,x);
	} else if (y<1) {
	    res = x;
	} else {
	    res = GCD.gcd(y,x-y);
	}
	return res;
  }
}