import java.util.*;
import java.io.*;
public class Main {
    public static void main(String[]args){
		Scanner sc = new Scanner(System.in);
		PrintWriter ou = new PrintWriter(System.out);
		int n = sc.nextInt();
		if(n == 0) ou.println("1.644934066848226436472");
		else{
		    double yono = 0;
		    for(int i = 1 ; i <= n ; i++){
		    	yono += 1.0 / i;
		    }
		    yono /= n;
		    ou.println(yono);
		}
		ou.flush();
	}
}