#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;


ll sumOfGroup(ll k) {
    // Return the sum of the elements of the k'th group.
    ll num=k*(k-1);
    num/=2;
    //ll a=1+num*2;
    
    ll sum=k*(2*num+k);
    return sum;
}

int main() {
    ll k;
    cin >> k;
    ll answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}