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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            MainStream();
        }
        static void MainStream()
        {
            Scan sc = new Scan();
            write wr = new write();

            int n = sc.intarr[0];
            int[] array = sc.intarr;

            double sum = 0;

            foreach(var a in array)
            {
                sum += 1.0 / a;
            }

            Console.WriteLine(1.0 / sum);
        }


    }

    class Scan
    {
        public string str => Console.ReadLine();

        public string[] strarr => str.Split(' ');

        public long[] longarr => strarr.Select(long.Parse).ToArray();
        public int[] intarr => strarr.Select(int.Parse).ToArray();
        public char[] chararr => str.ToArray();


    }



    class write
    {
        public void wri<Type>(Type x)
        {
            Console.WriteLine(x);
        }
    }

    class Method
    {
        static public int max(params int[] nums)
        {

            int maxx = nums[0];
            for (int i = 1; i < nums.Length; i++)
            {
                maxx = Math.Max(maxx, nums[i]);
            }
            return maxx;
        }
    }
}