#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define pb push_back
#define mp make_pair

int main()
{
	ll k;
	cin >> k;
	ll n=(k*(k-1))/2;
	ll a=1+(n-1)*2;
	a=a+2;
	ll ans=0;
	for(ll i=0;i<k;i++)
	{
	//	cout << a + 2*i << endl;
		ans+=a+2*i;
	}
	cout << ans << endl;
}