#include <bits/stdc++.h>

using namespace std;

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

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