namespace ConsoleApplication19
{
    class Account
    {
        private static Object thisLock = new Object();

        public void Withdraw()
        {
            lock (thisLock)
            {
                Console.WriteLine("1");
                Thread.Sleep(5000);
            }
        }
    }

    class Test
    {
        static void Main()
        {
            Account a = new Account();
            Thread t = new Thread(a.Withdraw);
            t.Start();

            Account b = new Account();
            Thread t2 = new Thread(b.Withdraw);
            t2.Start();

            Console.ReadLine();
        }
    }
}