#include<bits/stdc++.h>
using namespace std;
const int N = 2.5e5 + 5;
#define MOD 1000000007
#define lli long long int
#define ulli unsigned long long int
#define fr first
#define sc second
#define INF 1e9
#define L_INT 1e18
#define p_b push_back
#define m_p make_pair
#define plli pair <lli,lli>
#define pii pair<int,int> 
int ar[1000006]={0};
int main()
{
	lli count=1;
	for(int i=1;i<1000006;i++){
		ar[i]=count;
		count+=2;
	}
    lli k;
    cin>>k;
    k--;
    lli sum=0;
    
    count=(k*(k+1));
    count++;
    for(lli i=1;i<=k+1;i++){
    	sum+=count;
    	count+=2;
	}
	cout<<sum<<endl;
    return 0;
}