#include <iostream>
using namespace std;

int main() {
	long long int i, n, s=0, k=0;
    cin>>n;
 for(i=n-1;i>=1;i--)
      s=s+i;
 s=2*s+1;
 for(i=s;i<=s+(n-1)*2;i=i+2)
    k=k+i;
cout<<k;
	return 0;
}