import java.util.Scanner;
public class Q232499649 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
double sum = 0;
do {
sum += 1.0 / (n * n * n * n * n);
} while (--n >= 1);
System.out.println(sum);
}
}