using System;

public class Program

{

    public static void Main()

    {

        do {

            int temp;

            // Program start

            Console.WriteLine("Simple Calculator Program");

            Console.WriteLine("Type EXIT if you want to terminate the program");

            // First input

            Console.Write("Input First Number: ");

            string input = Console.ReadLine();

            if (input.Contains("exit") || input.Contains("Exit") || input.Contains("EXIT")){

               Console.WriteLine("Program has been terminated");

                break;

            } else if (input.Contains(".")){

               Console.WriteLine("Error: Use of decimals are not supported");

                break;

            } else if (!int.TryParse(input, out temp)){

                if (!input.Contains("exit") || !input.Contains("Exit") || !input.Contains("EXIT")){

                  Console.WriteLine("Error: Unfamiliar command");

                    break;

                }

            } 

            else {

               // Calculator

                // Converts first input into integer

               int num1 = Convert.ToInt32(input);

               Console.Write("Input Second Number: ");

                int num2 = Convert.ToInt32(Console.ReadLine());

               Console.Write("Input Third Number");

                int num3 = Convert.ToInt32(Console.ReadLine());

               // Adds all variables and prints sum

                int sum = num1 + num2 + num3;

                Console.WriteLine("The total sum is: {0}", sum);

                // Asks user to repeat or terminate the program

                Console.WriteLine("Would you like to use the program again? (Y/N)");

                string yn = Console.ReadLine();

                 if (yn.Contains("N") || yn.Contains("n")) {

                   Console.WriteLine("Thank you for using this program");

                     break;

                 }

            }

        } while(true);

    }

}