#include<bits/stdc++.h>
using namespace std;
int main( )
{
int n1,n2,n3,sum=0;
cin>>n1;
n3=n2=n1;
for (int i=1;i<=n3;i++)
{
sum=sum+n1*n2;
n1--;
n2=n1;
}
cout<<sum;
return 0;

}