using System;

using System.Threading;

​

public class LockStatement 

{ 

    public static void Main()

    {

        object gate = new object();

        int n = 0;

        var up = new Thread(() =>

        {

            for (int i = 0; i < 1000; i++)

            {

                Monitor.Enter(gate);

                try

                {

                    n++;

                }

                finally

                {

                    Monitor.Exit(gate);

                }

            }

        });

        up.Start();

        for (int i = 0; i < 1000; i++)

        {

            Monitor.Enter(gate);

            try

            {

                n--;

            }

            finally

            {

                Monitor.Exit(gate);

            }

        }

        up.Join();

        Console.WriteLine(n);

    }

}