#include <iostream>
using namespace std;
int main()
{
	int n = 0;
	cin >> n;
	int left = 1;
	int middle = 2;
	int right = 3;
	int series = 1*2;
	while (right < 2 * n) {
		left++;
		middle++;
		right++;
		series += left * middle * right;
	}
	cout << series << endl;
}