#17806: line 3 WA
rexwu1104@gmail.com
(黑雪公主 Black Lotus)
#include <iostream>
#include <string>
#include <algorithm>
#include <cmath>
using namespace std;
int main()
{
long long int a;
while (cin >> a) {
unsigned long long int n=(a+1)/2, num=(pow(n,2)*2-3)*3;
cout << num << endl;
}
}