public static void back(int size, int used, String path) {
		if (size == 0 && used != 2) {
			if (primes[1 + ring[sizeRing - 1]])
				out.append(path.substring(1) + "\n");
			return;
		}
		for (int i = 2; i <= sizeRing; i++)
			if ((used & (1 << i)) == 0 && primes[ring[size - 1] + i]) {
				ring[size] = i;
				back((size + 1) % sizeRing, used | (1 << i), path + " " + i);
				ring[size] = 0;
			}
	}