import java.util.*;
import java.io.*;
import java.math.*;
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();
		double yono = 0;
		for(int i = 1 ; i <= n ; i++){
			yono += 1.0 / i;
		}
		yono /= n;
		ou.println(yono);
		ou.flush();
	}
}