//Yukicoder
//Q71 そろばん

//二次元可変配列
//vector <vector <int>> mass;
//vector <vector <int>> memo;

//#include "stdafx.h"
#include <iostream>
#include <vector>
#include <list>//list
#include <set> //tree
#include <map> //連想配列
#include <unordered_set> //hash
#include <unordered_map> //hash
#include <algorithm>
#include <iomanip>

using namespace std;
typedef unsigned long long LL;


#define START (0)
#define RIGHT (1)
#define UP    (2)
#define LEFT  (3)
#define DOWN  (4)


vector <vector <int>> memo;
vector<int> a;
vector<int> q;
vector<int> flag;

#define DATA_MAX (1000000)

int main()
{
	LL N;
	LL n_up, n_down;
	LL total_down, total_up, all_total;
	LL max = 0;

	cin >> N;

	n_up = 0;
	n_down = N;
	while(1)
	{
		total_down = 1 * n_down;
		total_up = (n_down + 1) * n_up;

		all_total = total_down + total_up;
		if (max < all_total) max = all_total;
		n_up++;
		n_down--;
		if (n_up > N) break;
	}
	
	cout <<  max << endl;
	
	//getchar();
	return 0;
}