#include <iostream>
#include <vector>
#include <algorithm>
 
typedef long long ll;
 
ll solve(ll n) {
	ll answ = 0;
	for (int i = 0; ll(i) * (i+1) / 2 <= n; ++i) {
		answ += ll(i) * (i+1) / 2;
	}
	return answ;
}
 
int main() {
	ll n; std::cin >> n;
	std::cout << solve(n);
	return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>

typedef long long ll;

ll solve(ll n) {
    ll last = (std::sqrt(8 * n + 1) - 1) / 2;
    while (last * (last+1) / 2 > n) --last;
    while ((last+1) * (last+2) / 2 <= n) ++last;
    return last * (last+1) / 2 * (last+2) / 3;
}

int main() {
    ll n; std::cin >> n;
    std::cout << solve(n);
    return 0;
}