题目：

题解：

int countArrangement(int n) {
    int f[1 << n];
    memset(f, 0, sizeof(f));
    f[0] = 1;
    for (int mask = 1; mask < (1 << n); mask++) {
        int num = __builtin_popcount(mask);
        for (int i = 0; i < n; i++) {
            if (mask & (1 << i) && (num % (i + 1) == 0 || (i + 1) % num == 0)) {
                f[mask] += f[mask ^ (1 << i)];
            }
        }
    }
    return f[(1 << n) - 1];
}