#include <iostream>
using namespace std;
int main()
{
long long n;
cin >> n;
long long sum = 0;
long long a = 0, b = 1;
for (int i = 1; i <= n; i ++ )
{
b = i + a;
sum += b;
a = b;
}
cout << sum << endl;
}
#include <stdio.h>
int func(int n)
{
while(n>0)
{
return n*(1+n)/2+func(n-1);
}
return 0;
}
int main() {
int n = 0;
scanf("%d",&n);
int ret = func(n);
printf("%d",ret);
return 0;
}