#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k)
{
    long before = ((1 + (k - 1))*(k-1))/2;
    long first = before * 2 + 1;
    long sum = ((first + (first + 2 * (k - 1)))*k)/2;
    return sum;
}

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