public int filltheTruck(int num, List<Integer> boxes, int unitSize, List<Integer> unitsPerBox, int truckSize) {

	if (boxes.size() == 0 || unitsPerBox.size() == 0) return 0;

	PriorityQueue<Integer> pq = new PriorityQueue<Integer>(Collections.reverseOrder());
	for (int i = 0; i < boxes.size(); i++) {
		for (int j = 0; j < boxes.get(i); j++) {
			pq.add(unitsPerBox.get(i));
		}
	}

	int maxUnits = 0;
	while (truckSize > 0 && !pq.isEmpty()) {
		maxUnits += pq.poll();
		truckSize--;
	}

	return maxUnits;
}