#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long a = (long)k * (k - 1) + 1;
    long b = (long)k * (k + 1) - 1;
    long c = (a + b) * k / 2;
    return c;
}

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