#include <bits/stdc++.h>

using namespace std;
typedef long long unsigned ll;
ll sumOfGroup(ll k) {
    // Return the sum of the elements of the k'th group.
    ll n = k*(k-1);
    n = n+1;
    //cout<<n<<endl;
    ll ans=0;
    ans = k*(2*n+(k-1)*2);
    ans = ans/2;
    return ans;
}

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