#include<bits/stdc++.h>
using namespace std;
float h=0;
int a,d=1;
int main(){
   cin>>a;
    while(a>=d){
    	h=h+(1.0/d);
    	d++;	
    } 

     printf("%.3f",h);
}
/**************************************************************
	Problem: 1014
	User: chenyichuen
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/