using System;

​

public class Example

{

   public static void Main(string[] args)

   {

      int i,a,b,c;

       Console.WriteLine("Enter\n1. For add\n2. For sub");

       i=int.Parse(Console.ReadLine());

       Console.WriteLine("enter both no");

       a=int.Parse(Console.ReadLine());

       b=int.Parse(Console.ReadLine());

      switch (i)

      {

          case 1:

              c=a+b;

              Console.WriteLine("the sum is "+c);

              break;

          case 2:

              c=a-b;

              Console.WriteLine("the sub is "+c);

              break;

          default:

              Console.WriteLine("error");

              break;

      }

   }

}