import java.util.ArrayList;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;

class Bord {
    private ArrayList<String> kopper = new ArrayList<>();
    private Lock l?s = new ReentrantLock();
    private Condition ikkeTomt = l?s.newCondition();
    private int totaltAntallKopper;

    public Bord(int totaltAntallKopper) {
        this.totaltAntallKopper = totaltAntallKopper;
    }

    public void serverKaffe(String kaffe) {
        l?s.lock();
        try {
            kopper.add(kaffe);
            totaltAntallKopper--;
            ikkeTomt.signalAll();
        } finally {
            l?s.unlock();
        }
    }

    public String hentKaffe() throws InterruptedException {
        l?s.lock();
        try {
            while (kopper.isEmpty() && totaltAntallKopper > 0) {
                ikkeTomt.await();
            } 
            if (!kopper.isEmpty()) {
                return kopper.remove(0);
            }
            return null;
        } finally {
            l?s.unlock();
        }
    }
}