using System;

​

public class Program {

  public static void Main(string[] args) {

    do {

      Console.Write("h = ");

      string firstOperand = Console.ReadLine();

      int value = 0;

      bool gotResult = false;

​

      if (firstOperand == "exit") {

        Console.WriteLine("The program will not continue");

        break;

      } else {

        if (int.TryParse(firstOperand, out value)) {

          int h = Convert.ToInt32(firstOperand);

          do {

            if (gotResult) {

                break;

            }

            Console.Write("i = ");

            string secondOperand = Console.ReadLine();

            if (int.TryParse(secondOperand, out value)) {

              int i = Convert.ToInt32(secondOperand);

              do {

                Console.Write("j = ");

                string thirdOperand = Console.ReadLine();

                if (int.TryParse(thirdOperand, out value)) {

                  int j = Convert.ToInt32(thirdOperand);

                  int sum = h + i + j;

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

                    gotResult = true;

                  break;

                } else {

                  Console.WriteLine("Error.  Only accept integer value. ");

                }

              } while (true);

            } else {

              Console.WriteLine("Error.  Only accept integer value. ");

            }

          } while (true);

        } else {

          Console.WriteLine("Error. ");

        }

      }

    }

    while (true);

  }

}