#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long num = (double(1 + (k-1)) / 2) * (k - 1);
    long startValue = 1 + num*2;
    long res = 0;
    for (auto i = 0; i < k; ++i) {
            res = res + (startValue + i*2);
    }
    return res;
}

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