public Set<Unit> collectMinerals(Set<Unit> drones, Set<Unit> minerals) {
//		System.out.println("collectMinerals!");
		Set<Unit> claimedMinerals = new HashSet<Unit>();
		
		if (drones==null || drones.isEmpty() || minerals==null || minerals.isEmpty()){
			return claimedMinerals;
		}
		for (Unit drone : drones) {
			for (Unit mineral : minerals) {
				double distance = Math.sqrt(Math.pow(
						mineral.getX() - drone.getX(), 2)
						+ Math.pow(mineral.getY() - drone.getY(), 2));
//				System.out.println("distance: " + distance);
				if (distance < 300) {
					bwapi.rightClick(drone.getID(), mineral.getID());
					claimedMinerals.add(mineral);
					break;
				}
			}
		}
		return claimedMinerals;
	}