#include <iostream>
#include <cmath>

using namespace std;

double kocham_piwo(double n)
{
    if(n==1) return 0.5;
    else return (n/(n+1))+ kocham_piwo(n-1);


}

int main()
{
    double a;

    cin>>a;
    cout.precision(5);

    cout<<fixed<<kocham_piwo(a);

pawel


    return 0;
}