import java.util.*;
class A
{
   public static void main(String args[])
    {  
      long k,grp=1L,count=0;
      long i=1L;
      long sum=0L;
      Scanner ob=new Scanner(System.in);
      k=ob.nextLong();
      i=(k-1)*(k-1)+k;         
      while(count<k)
       {
         sum+=i;
         i+=2;
         count++;
       }
     System.out.println(sum);      
   }
       
}