public static void dfs(int row, int size, int[] queens) {
		if (row > size) {
			print_queen(size, queens);
			return;
		}
		for (int i = 1; i <= size; i++) {
			if (isValid(row, i, queens)) {
				queens[row] = i;
				dfs(row + 1, size, queens);
				queens[row] = 0;

			}
		}
	}