#include <bits/stdc++.h>

using namespace std;

unsigned long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    unsigned long inicio = (k * (k-1)) + 1;
    unsigned long count = 0;
    for(int i = 0; i< k; i++)
    {      
      count += inicio + (2*i);
    }
    return count;
}

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