SQUARES C++

#include<bits/stdc++.h>
using namespace std;

long long n,s,k;
int main()
{
    freopen("squares.inp","r",stdin);
    freopen("squares.out","w",stdout);
    cin>>n;
    k=2013*6;
    s=(((n%k)*((n+1)%k)*((2*n+1)%k))/6)%2013;
    cout<<s;
}