class Recursion {

  public static int factorial(int n) {
    System.out.println("    factorial called with n="+n);
    int toRet;
    if(n == 0) { toRet = 1; }
    else {
      int temp = factorial(n-1);
      toRet = n*temp;
      //return n*factorial(n-1);
    }
    System.out.println("    returning from factorial("+n+")");
    return toRet;
  } // End factorial()

  public static int fib(int n) {
    int toRet;
    System.out.println("    fib called with n="+n);
    if(n == 1) { toRet = 1; }
    else if(n == 2) { toRet = 1; }
    else { toRet = fib(n-1) + fib(n-2); }
    System.out.println("    returning from fib n="+n);
    return toRet;
  } // End fib()

  public static int gcd(int x, int y) {
    if(x < y) {
      int temp = x;
      x = y;
      y = temp;
    }
    return gcd_rec(x, y);
  }

  public static int gcd_rec(int x, int y) {
    if((x%y) == 0) { return y; }
    else {
      return gcd_rec(y, x%y);
    }
  } // End gcd_rec()

  public static void main(String[] args) {
    if(args.length != 2) {
      System.err.println("Usage: java Recursion <number-1> <number-2>");
      System.exit(1);
    }
    int arg1 = Integer.parseInt(args[0]);
    int arg2 = Integer.parseInt(args[1]);
    //System.out.println("    "+factorial(arg));
    System.out.println("    "+gcd(arg1, arg2));
  } // End main()

} // End class Recursion