#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
using namespace std;
#define ll long long
#define pb push_back
#define f first
#define s second
#define pp pair<long long,long long>
string str;
int main()
{
	ll n,t,i,j,k,l,m;
	cin>>k;
	l=k*(k+1);
	l--;
	ll ans=0;
	while (k--)
	{
		ans+=l;
		l-=2;
	}
	cout<<ans<<'\n';
	
	return 0;
}