做了三遍，最高是82分，我太难了。T_T

#include<bits/stdc++.h>
using namespace std;
int main(){
   long long a;
   unsigned long long b;
   cin>>a;
   b=(a*(a-1)*(a-2)*(a-3))/24;
   cout<<b;
   return 0;
}

求大佬T_T