114514

#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;
	}
}return 0;
}