#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;

ll last[200005]={-1};
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
    
	ll k;
	cin>>k;
    
    ll s=k-1;
    int i=1;
    ll sum=0;
    while(s--)
    {
    	sum=sum+i;
    	i++;
	}
	
	ll sum1=0;
	for(int i=0;i<k;i++)
	{
	    sum1=sum1+(2*sum+1);
		sum++;	
	}
	cout<<sum1<<endl;
}