对角线**交点**
by HoshinoYuki @ 2023-07-26 21:30:21
#改良了，还是有两个点没过
```cpp
#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main(){
long long n,N;
cin>>n;
N=n*(n-1)*(n-2)*(n-3)/24;
cout<<N;
return 0;
}
```
by qiang_di @ 2023-07-26 21:33:53
`n*(n-1)*(n-2)*(n-3)`溢出
by HoshinoYuki @ 2023-07-26 21:34:24
详见题解 1
by HoshinoYuki @ 2023-07-26 21:34:36
....题解也尝试过了，也爆了
by qiang_di @ 2023-07-26 22:00:10
用n*(n-1)/2*(n-2)/3*(n-3)/4
by jinxiyou @ 2023-11-04 15:14:10