hui

void ball() {
    int balls[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    int size = sizeof(balls) / sizeof(int);
    int k = 0;
    int h = 0;

    do {
        //h++;

        for (int i = 0; i < size; i++) {

            if (balls[i] == i) {
                k++;
                break;
            }

        }

    } while (next_permutation(balls, balls + size));

    cout << k << endl; //<< h << endl;
    system("pause");
    exit(1); return;
}