using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 namespace ConsoleApplication1
 {
     class Program
     {
         static void Main(string args)
         {
             DateTime start, end;
             TimeSpan total = TimeSpan.Zero;
             
             bool moveOn = true;
             int temp = 0;
             while(moveOn)
             {
             Console.WriteLine("enter start hour");
             start = DateTime.Parse(Console.ReadLine());
             Console.WriteLine("enter end hour");
             end = DateTime.Parse(Console.ReadLine());
             total += end - start;
             Console.WriteLine("To continue press 1, to terminate press 0");
             temp = int.Parse(Console.ReadLine());
             if (temp == 0)
             moveOn = false;
             }
             Console.WriteLine("total is: {0}", total);
         }
     }
 }