leetcode

0 class Solution {

1 public:

2 int countOrders(const int n) {

3 long res = 1, mod = (long)1E9 + 7;

4 for (int i = 1; i <= n; i++)

5 res = res * (i * 2 - 1) * i % mod;

6 return res;

7 }

8 };