#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
	long first = 1;
	for (long i = 1; i < k; ++i)
	{
		first = first + (i)*2;
	}
	long count = first;
	for (long i = 1; i < k; ++i)
	{
		first += 2;
		count += first;
	}
	return count;
}

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