#include<bits/stdc++.h>
using namespace std;
int n,i=1;
double s;
int main(){
	cin>>n;
	while(i<=n){ 
		if(i%2!=0) s=s+1.0/i;
		else s=s-1.0/i;
		i++;
	}
	cout<<fixed<<setprecision(4)<<s;
	return 0;
}
/**************************************************************
	Problem: 1521
	User: zhangziang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/