#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
double sum=0,n;
int i;
cin>>n;
for(i=1;i<=n;i++)
{
	if(i%2==1)
	sum+=(double)(1.0/i);
	else
	sum-=(double)(1.0/i);
}
printf("%.4f",sum);
}