import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		//Scanner um Werte a,b,c dynamisch einzulesen
		Scanner input = new Scanner(System.in); 

		int n = input.nextInt(); // a einlesen
		double result = 0.0; //DOUBLE UND NICHT INT!!!
		
		for (int i = 1; i <= n; i++) {
			result += 1/((double)i*i); //CONVERSION ZU DOUBLE WICHTIG!!!
		}
		
		System.out.println("Der Wert ist: " + result);
		
	}
	
}