#include <bits/stdc++.h>

using namespace std;

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

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