#include<iostream>
#include<cmath>
#include<cstdio>
#include<algorithm>
using namespace std;
int main(){
	int n;
	double res = 1;
	cin >> n;
	for(int i=1;i<=n;i++){
		long long res1 = 1;
		for(int j = 1;j<=i;j++){
			res1 *= j;
		}
		res += 1.0/res1;
	}
	printf("%.10lf",res);
	return 0;
}