#include<algorithm>

#include<cmath>

#include<cstdio>

#include<iostream>

using namespace std;

int main(){

int n;

cin>>n;

double p=1,q=2,sum=0;

for(int i=1;i<=n;i++){

sum+=q/p;

double qN=q+p,pN=q;

q=qN;

p=pN;

}

printf("%.4lf",sum);

return 0;

}