import java.util.*;
public class Main{
	public static void main(String args[]){
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		double a = 1.0;
		double sum = 0;
		for(int i = 1;i<=n;i++){
			if(i%2==0){
				 sum =sum-(a/i);
			}else{
				sum =sum+(a/i);
			}
		}
		System.out.println(String.format("%.4f",sum));
	}
}
/**************************************************************
	Problem: 1521
	User: admin
	Language: Java
	Result: Accepted
	Time:788 ms
	Memory:40532 kb
****************************************************************/