#include <bits/stdc++.h>

using namespace std;

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

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