#include<iostream>
using namespace std;
int main()
{
	unsigned long long n, S=0,s=1;
	cin >> n;
	for (int a = 1; a <= n; a++)
	{
		for (int b = 1; b <=a; b++)
		{
			s *= b;
			
		}
		S += s;
		s = 1;
	}
	
	cout << S;
	return 0;
}