#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

ll form(ll x){
    ll p = x+1;
    ll di = 2;
    return (x*p)/di;
}

ll sumOfGroup(ll k) {
    ll dis = form(k-1);
    ll fir = (dis*2);
    fir++;
    ll las = fir + (k*2);
    las-=2;
    return ((las+fir)/2)*k;
}

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