#include<iostream>
using namespace std;
int main()
{
   //A(n) = A(n-1) + 2(n-1)
   long long i,n,x;
   cin>>n;
   x = 2;
   if(n == 1){
      x = 2;
   }else{
      for(i = 2;i <= n;i++){
         x = x + 2 * (i - 1);           
      } 
   }
   cout<<x<<endl;
   return 0;
}
 
/**************************************************************
	Problem: 1355
	User: linmiaoling
	Language: C++
	Result: Wrong Answer
****************************************************************/