using System;

public class Program

{

    public static void Main()

    {

        Console.Write("Enter the first number: ");

        int firstnumber;

        firstnumber = Convert.ToInt32(Console.ReadLine());

        Console.Write("Enter second number: ");

        int secondnumber;

        secondnumber = Convert.ToInt32(Console.ReadLine());

        Console.Write("What operation do you want to perform?: ");

        Console.WriteLine("a.addition b.subtraction c.multiplication d.division");

        string operation = Console.ReadLine();

        if(operation == "a"){

            Console.WriteLine("You choose to perform addition");

            Console.WriteLine("Here is your output: " + "{0} + {1} = {2}", firstnumber, secondnumber, firstnumber+secondnumber);

        }

        if(operation == "b"){

            Console.WriteLine("You choose to perform subtraction");

            Console.WriteLine("Here is your output: " + "{0} - {1} = {2}", firstnumber, secondnumber, firstnumber-secondnumber);

        }

        if(operation == "c"){

            Console.WriteLine("You choose to perform multiplication");

            Console.WriteLine("Here is your output: " + "{0} * {1} = {2}", firstnumber, secondnumber, firstnumber*secondnumber);

        }

        if(operation == "d"){

            Console.WriteLine("You choose to perform division");

            Console.WriteLine("Here is your output: " + "{0} / {1} = {2}", firstnumber, secondnumber, firstnumber/secondnumber);

        }

​

    }

}