#include <bits/stdc++.h>

using namespace std;
using ull = unsigned long long;

int main(){
    ull N;
    cin >> N;
    ull ans = 0;
    ull a = sqrt(N);//整数型において、sqrt(x)はxの平方根の切り捨て
    ull b = 0;
    for(ull i = 1;i <= a;i++)b += i;//1 + 2 + ... + a

    for(ull i = 0;i < a;i++){
        ans += i * a * a + b;//ia^2+b
    }

    for(ull i = a * a + 1;i <= N;i++)ans += i;//(a^2+1) + (a^2+2) + ... + N

    cout << ans << endl;
}