#include <iostream>
using namespace std;
int main()
{
	long int g = 0,n,ans=0;
	cin >> n;
	long int temp=0, Temp=0;
	for (int j = 0; j <= n; j++)
	{
		g = j;
		temp = Temp = g;
		for (int i = 0; i < Temp - 1; i++)
		{
			temp = temp * (g - 1);
			g -= 1;
		}
		ans += temp;
	}
	cout << ans;
	return 0;
}