#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long k) {
    if (k == 1) return 1;
    // Return the sum of the elements of the k'th group.
    long long prev = (k * (k-1)) >> 1;
    long long first = 1 + prev * 2;
    long long additions = 2 * prev;
    return first * k + additions;
}

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