import java.util.*;
import java.lang.*;
import java.io.*;
 
class Ideone
{
	public static void main (String[] args) {
		double f = 1;
		double p = 1;
		Scanner in=new Scanner(System.in);
		int n = in.nextInt();
	for(int i = 1; i <= n; i++)
	{ 
		f = f * i;
		p *= ( 1 / f  + 2);
	}
 System.out.println(p);
	}
}