làm bằng c++ mình cần gấp mn ơi

$\color{green}{\texttt{C}}\color{lightgreen}{\texttt{+}}\color{lightgreen}{\texttt{+}}$

#include <iostream>

using namespace std;

int main() {
  long long n; cin >> n;
  cout << (n % 12126 * ((n+1) % 12126) * ((2 * n+1) % 12126) / 6) % 2021;
}

$\\$
\begin{array}{c|c|c}\color{#ffd710}{\texttt{\{}} \color{#8655d6}{\texttt{\{}}\ \ \color{#8cdcda}{\text{Daoanhviet96}}\ \ \color{#8655d6}{\texttt{\}}} \color{#ffd710}{\texttt{\}}}\end{array}

#include <bits/stdc++.h>
#define ll long long
const int mod=2021;
using namespace std;
int main() {
    ll n;
    cin >> n;
    ll ans = ((((n%mod)*((n+1%mod))%mod)*((2*n+1)%mod)%mod)*337)%mod;
    cout << ans;
    return 0;
}