#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
   long l;
   long sum;
    l = 1+(k-1)*k/2;
    sum = k*(l*2+k-2);
    return(sum);
    // 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;
}