class Main {
    static public void main (String argv[]) {
        Connector c1, c2, c3;
        c1 = new Connector(); 
        c2 = new Connector();
        c3 = new Connector();

        Stage s1, s2;
        Listener l;
        s1 = new Stage(1, c1, c2);
        s2 = new Stage(2, c2, c3);
        l  = new Listener(c3);

        s1.start();
        s2.start();
        l.start();

        for (int i=1; i<2; i=i+1) c1.add(i);
        c1.stop(); 
    }
}

class Connector {
    public int queue = -1;
    public synchronized int take(){
        int value;
        while ( queue < 0 )
            try {wait();} catch (InterruptedException ex) {}
        value = queue; queue = -1; return value;
    }
    public synchronized void add(int o) { queue = o; notifyAll(); }
    public synchronized void stop(){ queue = 0; notifyAll(); }
}

class Stage extends Thread {
    int id; Connector c1, c2;
    int stop = -1;
    public Stage(int i, Connector a1, Connector a2)
        { id = i; c1 = a1; c2 = a2; }
    public void run() {
        int tmp = -1;
        while (tmp != 0)
            if ((tmp=c1.take()) != 0){
                c2.add(tmp+1);
            }
        stop = 0;
        c2.stop();
    }
}

class Listener extends Thread {
    Connector c;
    int stop = -1;
    public Listener(Connector con) { this.c = con; }
    public void run(){
        int tmp = -1;
        while (tmp != 0)
            if ((tmp=c.take()) != 0);
        stop = 0;
        System.out.println("Listener stop.");
    }
}