using System;

​

public class Maths {

​

  public static void Swap(ref int a, ref int b) {

    int temp = a;

    a = b;

    b = temp;

  }

​

  public static void Swap(ref string a, ref string b) {

    string temp = a;

    a = b;

    b = temp;

  }

}

​

public class Program {

  public static void Main() {

    int twenty = 20;

    int thirty = 30;

    string forty = "forty";

    string fifty = "fifty";

    Maths.Swap(ref twenty, ref thirty);

    Console.WriteLine("twenty = {0}", twenty);

    Console.WriteLine("thirty = {0}", thirty);

​

    Maths.Swap(ref forty, ref fifty);

    Console.WriteLine("forty = {0}", forty);

    Console.WriteLine("fifty = {0}", fifty);

​

  }

}