#include <bits/stdc++.h>

using namespace std;

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

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