#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    if (k == 1)
        return 1;

    long long int s = 0;
    s = k * (k - 1) + 1;
    long long int r = (s + s + (k - 1) * 2);
    r = r * k;
    r = r/2;
    return r;
}

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