public void Run()
            {
                Task t1 = Task.Factory.StartNew(() => c.Run());
                Task t2 = Task.Factory.StartNew(() => b.Run());

                Task.WaitAll(t1, t2);
            }
        // Task 4: Sleeping Barber
        public static void RunTask4(int maxClientsCount)
        {
            var barberShop = new BarberShop(maxClientsCount);
            var barber     = new Barber(barberShop);
            var client     = new Client(barberShop);

            Task.WaitAll(barber.Run(), client.Run());
        }