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

class Monitor {

    private LinkedList<Integer> tallArray = new LinkedList<Integer>();
    private Lock laas = new ReentrantLock();
    private Condition tomt = laas.newCondition();
    private int antallSettInn;

    public Monitor(int antallSettInn){
        this.antallSettInn = antallSettInn;
    }

    public void ferdig(){
        laas.lock();
        try{
            antallSettInn--;
        }finally{
            laas.unlock();
        }
        
    }

    public void settInnTall(int tall){
        laas.lock();
        try{
            tallArray.add(tall);
            tomt.signalAll();
        }finally{
            laas.unlock();
        }
    }


    public ArrayList<Integer> taUtToTall(){
        laas.lock();
        try {
            while(tallArray.size() < 2){
                if(antallSettInn == 0) return null;
                tomt.await();
            }
            ArrayList<Integer> returTall = new ArrayList<Integer>();
            returTall.add(tallArray.remove(0));
            returTall.add(tallArray.remove(0));
            return returTall;
        } catch (InterruptedException e) {
            return null;
        }finally{
            laas.unlock();
        }
    }
    
}