public int countArrangement(int N) {

int[] count = new int[1];

helper(N, 1, new boolean[N + 1], count);

return count[0];

}

private void helper(int N, int k, boolean[] visited, int[] count) {

if (k > N) {

count[0]++;

return;

}

for (int i = 1; i <= N; i++) {

if (!visited[i] && (i % k == 0 || k % i == 0)) {

visited[i] = true;

helper(N, k + 1, visited, count);

visited[i] = false;

}

}

}