#include<stdio.h>
#include<stdlib.h>
#include<math.h>

double sum(int n)
{
	double s;
	s = (double)pow(-1,n-1) * pow(2,n);
	s /= (double)(pow(2,n) + pow(-1 , n));
	s /= (double)(pow(2,n+1) + pow(-1 , n+1));
	return s;
}

int main()
{
	int n,i=0;
	double s;
	scanf("%d",&n);
	for(i=1;i<=n;i++){
		s += sum(i);
	}
	printf("%.6lf",s);
	return 0;
}