static void Main(string[] args) { Clock clock = new Clock(); User al = new User("Alexander"); bool isWorking = true; while (isWorking) { Console.WriteLine("1)Set time 2)Subscribe 3)Unsubscribe 4)Turn On"); string key = Console.ReadLine(); switch (key) { case "1": { Console.WriteLine("Enter Countdown time"); clock.SetSeconds(int.Parse(Console.ReadLine())); } break; case "2": { al.Subscribe(clock); } break; case "3": al.UnSubscribe(clock); break; case "4": { clock.BeginTicks(); } break; default: isWorking = false; break; } Console.WriteLine("Press any key to continue"); Console.ReadKey(); Console.Clear(); } }