using System;

public class Program

{

    public static void Main()

    {

        int a = 10, b=20;

        Console.WriteLine("Before swap\n a="+a+" \n b=" +b, a,b);

        a=a+b;

        b=a-b;

        a=a-b;

        Console.WriteLine("\nAfter swap \n a="+a+ " \n b="+b, a,b);

    }

}