#include<iostream>
using namespace std;
int main() {
int n;
cin >> n;
int sum = 0;
for (int i = 1; i <= n; i++) {
sum += (3 * i - 1);
}
cout << sum << endl;
return 0;
}
#include<iostream>
using namespace std;
int main() {
int n;
cin >> n;
int sum = 0;
for (int i = 1; i <= n; i++) {
sum += (3 * i - 1);
}
cout << sum << endl;
return 0;
}