g488. COVID-101 | From: [36.235.70.41] | 發表日期 : 2024-04-07 00:09

#include<bits/stdc++.h>

using namespace std;

int s(int n)

{

if(n==1) return 1;

else return s(n-1)+n*n-n+1;

}

 

int main()

{

int n;

cin>>n;

cout<<s(n)<<endl;

}