#include <stdio.h>
#include <stdlib.h>
int main()
{
int n;
scanf("%d",&n);
double ans=0;
if(n%2==1)
for(int k=1;k<=n;k+=2) ans+=1.0/k;
}
else
for(int k=2;k<=n;k+=2) ans+=1.0/k;
return printf("%f\n",ans),0;