include <bits/stdc++.h>
using namespace std;
int main() {
int n, s = 0, k = 0 ;
cin >> n;
for (int i = 0; i < n; i++) {
s += i;
k += i * i;
if (s >= n) {
s = s - n;
k -= s * i;
cout << k << endl;
return 0;
}
if (n == 1) {
cout << "1" << endl;
}
}
return 0;
}