#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    //first no is 2*k+1
    //k/2(2*a+(k-1)*2);
    //if k*(k+1)/2+1 th
    //1+k*(k+1)
   long p= k*(2*(1+k*(k-1))+(k-1)*2)/2;
    return p;
    // Return the sum of the elements of the k'th group.
}

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