using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Type first number...");

        int firstnum = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("Select Operation *,/,+,-");

        string sum = Console.ReadLine();

        Console.WriteLine("Type second number...");

        int secondnum = Convert.ToInt32(Console.ReadLine());

        if (sum == "+")

        {

            Console.WriteLine("Answer: {0}",firstnum+secondnum);

        }

        if (sum == "-")

        {

            Console.WriteLine("Answer: {0}",firstnum-secondnum);

        }

        if (sum == "*")

        {

            Console.WriteLine("Answer: {0}",firstnum*secondnum);

        }

        if (sum == "/")

        {

            Console.WriteLine("Answer: {0}",firstnum/secondnum);

        }

    }

   }

​