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

int main(){
	int n, b;
	double fatorial=1, conta=0;

	cin >> n;

	n--;

	while(n>=0){
		b = n;
		n--;
		fatorial=1;
			while(b>0){

				fatorial = fatorial * b;
				b--;
			}
		conta += (1/fatorial);
		}
	cout << conta;

	return 0;

}