#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
	double e=1,n,l;
	int i,j;
	cin>>n;
	for(i=1;i<=n;i++)
	{
		l=1;
	for(j=1;j<=i;j++)
	{
		l*=j;
	}
	e+=(double)(1/l);	
	}
	printf("%.10lf",e);
}