class Increment extends Thread{
     static Integer i=new Integer(0);

    public void run(){

        for(int j=1;j<=1000;j++){
            synchronized (i) {
                i++;
            }
        }

    }
}


public class Puzzle {
    public static void main(String args[]) {
        Thread t1=new Increment();
        Thread t2=new Increment();
        t1.start();
        t2.start();
        try {
            t1.join();
            t2.join();
        }catch (InterruptedException r){}
        System.out.println(Increment.i);
    }
}