#include <iostream>

long int sumGroup(long int k) {
	long int startNum = k * k - (k - 1);
	long int endNum = k * k + (k - 1);

	return (startNum + endNum) * k / 2;
}

int main() {
	long int k;
	std::cin >> k;
	std::cout << sumGroup(k) << std::endl;

	return 0;
}