#include <bits/stdc++.h>

using namespace std;

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

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