#39858: recursive
mu0975353917@gmail.com
(Moon Chan)
#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;
}