How to find HCF/GCD with C#?

using System;

public class Test
{
  private static int HCF(int x, int y)
  {
     if (0 == x) return y;
     if (0 == y) return x;
     if (x == y) return x;
     if (x < y) return HCF(x, y-x);
     return HCF(x-y, y);
  }
  private static int GCD(int x, int y)
  {
     if (0 == y) return x;
     return GCD(y, x % y);
  }
  public static void Main(string[]args)
  {
    int x = 14, y = 18;
    Console.WriteLine("HCF of {0} & {1} is {2}", x, y, HCF(x, y));
    Console.WriteLine("GCD of {0} & {1} is {2}", x, y, GCD(x, y));
  }
}