#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;

int n;
double ans,k,k2,add;

inline void read(int &x);

int main()
{
	read(n);
	
	ans=add=420000.0/n; k=1;
	
	for(int i=2; i<=n; i++)
	{
		k=(1-k2)/2;
		k2=k/2;
		ans+=add*k;
	}
	printf("%.2lf\n",ans);
	
	return 0;
}

inline void read(int &x)
{
	x=0;
	int s=1;
	char c=getchar();
	while(c<'0' || c>'9') {if(c=='0') s=-1; c=getchar();}
	while(c>='0' && c<='9') {x=x*10+c-'0'; c=getchar();}
	
	x*=s;
}