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 < 10000; i++)

                lock (gate)

                    n++;

        });

        up.Start();

        for (int i = 0; i < 10000; i++)

            lock (gate)

                n--;

        up.Join();

        Console.WriteLine(n);

    }

}