#include <bits/stdc++.h>

using namespace std;

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

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