#include<stdio.h>
int main()
{
	int n,i = 1,s1=0;
	scanf("%d",&n);
	double s = 0.0;
	while(i<=n)
	{
		s1=s1+i;
		i++;
		s=s+1.0/s1;
		
		
	}
	printf("%llf",s);
	return 0;
}