#include<bits/stdc++.h>
using namespace std;
int f1(int n)
{
	int r=0;
	if(n==1 || n==2)
	{
		r=1;
	}
	else
	{
		r=f1(n-1)+f1(n-2);
	}
	return r;
}
int main()
{
	int n;
	cin>>n;
	float k=0;
	float h=0;
	for(int i=1;i<=n;i++)
	{
		k=f1(i)*1.0/f1(i+1);
		h+=k;
	}
	printf("%.3f",h);
	return 0;
}
/**************************************************************
	Problem: 1147
	User: chenkexin
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/