#include<bits/stdc++.h>
using namespace std;
int n,s;
int f(int n){
	int r;
	if(n==1||n==2)r=1;
	else{
		r=f(n-1)+f(n-2);
		return r;
	}
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		s=s+f(i)*1.0/f(i+1);
	}
	printf("%.3f",s);
	return 0;
}

/**************************************************************
	Problem: 1147
	User: wuzhijing
	Language: C++
	Result: Wrong Answer
****************************************************************/