private void keys(STNode<Key, Value> x, LinkedList<Key> list, Key lo, Key hi)
	{
		if (x == null)
			return;

		int cmplo = lo.compareTo(x.key);
		int cmphi = hi.compareTo(x.key);

		if (cmplo < 0) // if lo is lesser than the key
			keys(x.left, list, lo, hi);
		if (cmplo <= 0 && cmphi >= 0) // if key is inbetween lo and hi
			list.add(x.key);
		if (cmphi > 0) // if hi is greater than key
			keys(x.right, list, lo, hi);
	}