#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    // n(n+1)/2
    long n = k-1;
    cerr << "n = " << n << endl;
    // x is starting index
    long x = n * (n+1) / 2;
    cerr << "x = " << x << endl;
    long start = x * 2 + 1;
    cerr << "start = " << start << endl;
    long count = k * (k-1) / 2;
    cerr << "count = " << count << endl;
    long total = start * k + k*(k-1);
    return total;
}

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