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;

}