#include <bits/stdc++.h>

using namespace std;

typedef unsigned int ui;
typedef unsigned long long ul;
typedef long long sl;

int main(int argc, char* argv[])
{
	ios_base::sync_with_stdio(false);

	ul k;
	cin >> k;

	ul s = k * (k - 1) / 2 + 1,
	   c = 2 * s - 1;

	ul cs = (c + (k - 1)) * k;
	cout << cs << endl;
	return 0;
}