import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    }
} Main public static void main(String[] args) throws Exception {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    } main {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    } Scanner in = new Scanner(System.in); in new Scanner(System.in) int num = in.nextInt(); num in.nextInt() in.nextInt in double[] arr = new double[num]; arr new double[num] num double max = 0; max 0 double sum = 0; sum 0 for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        } int i = 0; int i = 0; i 0 i < num i num i++ i++ i {
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        } {
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        } arr[i] = in.nextDouble() arr[i] arr i in.nextDouble() in.nextDouble in if (max < arr[i]){
                max = arr[i];
            } max < arr[i] max arr[i] arr i {
                max = arr[i];
            } max = arr[i] max arr[i] arr i for (int i = 0;i < num;i++){
            sum += max / arr[i];
        } int i = 0; int i = 0; i 0 i < num i num i++ i++ i {
            sum += max / arr[i];
        } {
            sum += max / arr[i];
        } sum += max / arr[i] sum max / arr[i] max arr[i] arr i System.out.println(max/sum) System.out.println System.out System System.out max/sum max sum String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        // Your code here!
        
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        double[] arr = new double[num];
        double max = 0;
        double sum = 0;
        for (int i = 0;i < num;i++){
            arr[i] = in.nextDouble();
            if (max < arr[i]){
                max = arr[i];
            }
        }
        for (int i = 0;i < num;i++){
            sum += max / arr[i];
        }
        System.out.println(max/sum);

        
    }
}
