#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long k_l = k - 1;
    long start = (long) k_l * (1 + k_l) / 2;
    long sum = (long) k * ( (2 * start) + 1 + (2 * (k_l + start) + 1) ) / 2;
    return sum;
}

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