using System;

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        int no1 = 10;

        int no2 = 20;

        Console.WriteLine("No1 = {0}  No2 = {1}", no1, no2);

       // Console.WriteLine( "No2 =" + " " + no2);

        SwapNum(ref no1, ref no2);

        Console.WriteLine("After sawapping");

        Console.WriteLine("No1 = {0}  no2 = {1}", no1, no2);

       // Console.WriteLine("No2 =" + " " + no2);

    }

    static void SwapNum(ref int x, ref int y)

    {

      x = x + y;

      y = x - y;

      x = x - y;        

    }

}