#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long int k) {
    // Return the sum of the elements of the k'th group.
     long   sum=0;
   long   no=(k-1)*(k)/2;
  long   nodd=1+no*2;
    sum=k*(2*nodd+(k-1)*2)/2;
    return sum;
}

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