#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long long k) {
    long long s=k*(k-1)+1;
    return k*(2*s+(k-1)*2)/2;
}

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