class Counter {
    private int _val;

    public Counter(int n) {
        _val = n;
    }

    public void inc() {
        _val++;
    }

    public void dec() {
        _val--;
    }

    public int value() {
        return _val;
    }
}

class Mutex {
    public int whosTurn = 0;
    public boolean[] interested = {false, false};
}

class IThread extends Thread {
    private Counter cnt;
    private Mutex mutex;


    public IThread(Counter cnt, Mutex mutex) {
        this.cnt = cnt;
        this.mutex = mutex;
    }

    public void run() {
        for (int i = 0; i < 10000; i++) {
            mutex.interested[0] = true;
            mutex.whosTurn = 1;
            while (mutex.interested[1] && mutex.whosTurn == 1) {}

            cnt.inc();
            mutex.interested[0] = false;
        }
    }
}

class DThread extends Thread {
    private Counter cnt;
    private Mutex mutex;

    public DThread(Counter cnt, Mutex mutex) {
        this.cnt = cnt;
        this.mutex = mutex;
    }

    public void run() {
        for (int i = 0; i < 10000; i++) {
            mutex.interested[1] = true;
            mutex.whosTurn = 0;
            while (mutex.interested[0] && mutex.whosTurn == 0) {}

            cnt.dec();
            mutex.interested[1] = false;
        }
    }
}

public class Race {
    public static void main(String[] args) throws InterruptedException {
        Counter cnt = new Counter(0);
        Mutex mutex = new Mutex();

        Thread iThread = new IThread(cnt, mutex);
        Thread dThread = new DThread(cnt, mutex);

        iThread.start();
        dThread.start();

        iThread.join();
        dThread.join();

        System.out.println("stan=" + cnt.value());
    }
}