Problem:
Score : 200 points

Problem Statement

Given is a sequence of N integers A_1, \ldots, A_N.

Find the (multiplicative) inverse of the sum of the inverses of these numbers, \frac{1}{\frac{1}{A_1} + \ldots + \frac{1}{A_N}}.

Constraints

1 \leq N \leq 100

1 \leq A_i \leq 1000

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 \ldots A_N

Output

Print a decimal number (or an integer) representing the value of \frac{1}{\frac{1}{A_1} + \ldots + \frac{1}{A_N}}.

Your output will be judged correct when its absolute or relative error from the judge's output is at most 10^{-5}.

Sample Input 1

2
10 30

Sample Output 1

7.5

\frac{1}{\frac{1}{10} + \frac{1}{30}} = \frac{1}{\frac{4}{30}} = \frac{30}{4} = 7.5.

Printing 7.50001, 7.49999, and so on will also be accepted.

Sample Input 2

3
200 200 200

Sample Output 2

66.66666666666667

\frac{1}{\frac{1}{200} + \frac{1}{200} + \frac{1}{200}} = \frac{1}{\frac{3}{200}} = \frac{200}{3} = 66.6666....

Printing 6.66666e+1 and so on will also be accepted.

Sample Input 3

1
1000

Sample Output 3

1000

\frac{1}{\frac{1}{1000}} = 1000.

Printing +1000.0 and so on will also be accepted.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

  import java.util.*;
 
  public class Main {
      public static void main (String[]args){
 
          Scanner scanner = new Scanner(System.in);
          
          int N = scanner.nextInt();
 
          int cnt = 0;
 
          List <Integer> AList  = new ArrayList<Integer>();
 
          // 入力数に従って標準入力
          while (cnt < N){
 
            Integer A = scanner.nextInt();
 
            AList.add(A);
 
             cnt = cnt + 1;
          }
          
          scanner.close();
 
          List <Double> DList  = new ArrayList<Double>();
          
          // 逆数への変換
          for (Integer A :AList){
            double d = 1 / A;
 
            DList.add(d);
          }
 
          // 逆数を総和
          Double dAll = 0.0;
          for (Double d:DList){
            dAll += d;
          }
 
          // 総和を逆数とする
          Double result = 1 / dAll;
          
          // 出力
          System.out.println(result);
                  
      }
  }