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: Accepted)

import java.io.*;
import java.util.*;

public class Main{
    
    public static void main(String[] args) throws IOException {
        Reader.init();
        int N=Reader.nextInt();
      	int A[]=new int[N];
      	read(A, N);
      	double sum=0;
      	for(int i:A){
        	sum+= (double)1/i;
          	//print("i: "+i);
          	//print("Sum: "+sum);
        }
      	print(1/sum);
      
    }

    static int mod=1000000007;
    
    public static void read(int arr[], int N) throws IOException{ for(int i=0;i<N;i++){ arr[i]=Reader.nextInt(); } }
    public static void read(String arr[], int N) throws IOException{ for(int i=0;i<N;i++){ arr[i]=Reader.next(); } }
    
    public static void print(Object O){ System.out.println(O); }
    
    public static void display(int arr[]){ System.out.println(Arrays.toString(arr)); }
    public static void display(int arr[][], int N){ for(int i=0;i<N;i++){ System.out.println(Arrays.toString(arr[i])); } }
  
}

class Reader {
    static BufferedReader reader;
    static StringTokenizer tokenizer;

    static void init() {
        reader=new BufferedReader(new InputStreamReader(System.in));
        tokenizer=new StringTokenizer("");
    }

    static String next() throws IOException {
        while (!tokenizer.hasMoreTokens() ) {
            tokenizer=new StringTokenizer(reader.readLine());
        }
        return tokenizer.nextToken();
    }

    static int nextInt() throws IOException { return Integer.parseInt(next()); }
    static double nextDouble() throws IOException { return Double.parseDouble(next()); }
    static long nextLong() throws IOException { return Long.parseLong(next()); }
    static String nextLine() throws IOException { return reader.readLine(); }
}