#include<iostream>
using namespace std;
int main(){
	long long int k,p,sum = 0,l = 1; 
	cin >> k;
	p = (k * (k -1)) / 2;
	for(int i = 0;i < k;i++){
		sum = sum + ((2 * p) + l);
		l = l + 2;
	}
	cout << sum << endl;
	return 0;
}