import java.util.Scanner;

public class WangDao {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		System.out.print("Input the number: ");
		int n = scan.nextInt();
		double sum = 0;
		if (n % 2 == 0) {
			sum = evenNumber(n);
		} else {
			sum = oddNumber(n);
		}
		System.out.println("The sum is " + sum);
	}
	
	public static double evenNumber(int n) {
		double sum = 0;
		
		for (double i = 2; i <= n; i = i + 2) {
			sum += 1 / i;
		}
		
		return sum;
	}
	
	public static double oddNumber(int n) {
		double sum = 0;
		
		for (double i = 1; i <= n; i = i + 2) {
			sum += 1 / i;
		}
		
		return sum;
	}
}