#include <bits/stdc++.h>

using namespace std;

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

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