using System;

    class Program

    {

        static void Main(string[] args)

        {

            do

            {

                Console.Write("x = ");

                string str = Console.ReadLine(); if (str == "exit")

                {

                    Console.WriteLine("Program has stopped"); 

                    break;

                }

                else

                {

                    int x = Convert.ToInt32(str); Console.Write("y = ");

                    int y = Convert.ToInt32(Console.ReadLine()); int sum = x + y;

                    Console.WriteLine("Result: {0}", sum);

                }

            }

            while (true);

        }

    }

​