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

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

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

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

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