#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
   long b = k*(k - 1)+1;
	long su = b+(k-1)*2;

	return k*(su+b)/2;
}

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