#include <bits/stdc++.h>

#define DEBUG

using ll = long long;
ll constexpr INF = 1e18;

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(NULL);

    ll k;
    std::cin >> k;
    ll temp = k * (k - 1) + 1;

    ll sum = 0;
    for (int i = 0; i < k; ++i) {
        sum += temp;
        temp += 2;
    }

    std::cout << sum << '\n';
}