#include <bits/stdc++.h>

using namespace std;

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

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