#include<bits/stdc++.h>
#include <cstdio>
#define LL long long

using namespace std;
LL A[100009];
int main()
{
 // freopen("imput.txt","r",stdin);
  


  LL ans=0,k,k1;
  cin>>k;

  k1 = (k*(k-1));
  k1++;
  LL sum=0;
  for (int i = 0; i < k; ++i)
  {
  	sum+=k1;
  	k1+=2;
  }




  cout<<sum<<endl;
  
  return 0;
}