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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function Main(input){
  var inputs = input.split("\n");
  var array = inputs[1].split(" ");
var N = inputs[0]-1;
  var sum = 0;
var i;
  for(i = 0;i <= N;i++){
    sum = sum + new Number(array[i]);
 }
  var plo;
  for(j = 0;j <= N;j++){
    if(plo == undefined){
      plo =new Number(array[j]);
    }
    plo = plo*new Number(array[j]);
  }
  var mom = 0;
  for(k = 0;k <= N;k++){
    mom = mom + plo/new Number(array[k]);
  }
  console.log(plo/mom);
  }
  Main(require('fs').readFileSync('/dev/stdin','utf8'));