You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
|
#include <bits/stdc++.h>
|
|
|
|
using namespace std;
|
|
//公式！重要的是公式！
|
|
int main() {
|
|
ios::sync_with_stdio(false); //读入输出优化的强迫症
|
|
unsigned long long n;
|
|
cin >> n;
|
|
cout << (n * (n - 1) / 2 * (n - 2) / 3 * (n - 3) / 4) << endl;
|
|
return 0;
|
|
} |
