#include<iostream>

using namespace std;

int main()
{
	int n;
	cout << "N : ";
	cin >> n;
	
	float e = 1;
	int F = 1;
	
	for (int i=2; i<=n; i++)
	{
		F *= i;
		e += 1.0/F;
	}
	
	cout << "\ne = " << e;
	
	return 0;
}