#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: 1366
	User: admin
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/