void expand(int c, int n, List<Integer> list) {
		if (c == n)
			return;
		else {
			for (int i = list.size() - 1; i >= 0; i--) {
				int a = list.get(i);
				a = a | (1 << (c));
				list.add(a);
			}
			expand(c + 1, n, list);
		}
	}