//Dennis Matveyev for SER 2013
//The Days of Christmas

/* Idea:  Notice the pattern
1, 4, 10 ... dealing with sums ... looks familiar.  Pascal's Triangle or N choose K notation

Solution:
populate array with values = 1 2 3 4 5 6 7 8 9 10
do the summation of current + previous values:  1 3 6 10 15 21 28 36 45 55
repeat:  1 4 10 20 35 56 84 120 165 220

Output appropriate step.
*/


#include <iostream>
#include <vector>
using namespace std;

int main()
{
	int n;
	vector<int> v(1000001);

	v[1] = 1;
	for (int i = 2; i <= 1000000; i++) v[i] = i;
	for (int i = 2; i <= 1000000; i++) v[i] += v[i - 1];
	for (int i = 2; i <= 1000000; i++) v[i] += v[i - 1];

	while (cin >> n && n > 0) cout << v[n] << endl;

	return 0;
}