#include <cstdlib>
#include <iostream>

using namespace std;

int main()
{
int n,i,br;
cout<<„Unesi redni broj koraka, n= „;
cin>>n;
br=1;
for(i=0;i<n;i++)
br=br+i*6;
cout<<br<<endl;
system(„PAUSE“);
return EXIT_SUCCESS;
}