import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    }
} Main public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    } main {
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) scanner.nextLine() scanner.nextLine scanner String[] paramsA = scanner.nextLine().split(" "); paramsA scanner.nextLine().split(" ") scanner.nextLine().split scanner.nextLine() scanner.nextLine scanner " " scanner.close() scanner.close scanner double denominator = 0; denominator 0 for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        } String a paramsA {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        } {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        } denominator += (double)1 / (double)(Integer.parseInt(a)) denominator (double)1 / (double)(Integer.parseInt(a)) (double)1 (double)(Integer.parseInt(a)) Integer.parseInt Integer a System.out.println(String.valueOf(((double)1 / denominator))) System.out.println System.out System System.out String.valueOf(((double)1 / denominator)) String.valueOf String ((double)1 / denominator) (double)1 denominator String[] args args public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    }
} public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
        String[] paramsA = scanner.nextLine().split(" ");
        scanner.close();

        double denominator = 0;
        
        for (String a: paramsA) {
            denominator += (double)1 / (double)(Integer.parseInt(a));
        }

        System.out.println(String.valueOf(((double)1 / denominator)));
    }
}