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, $\frac{1}{\frac{1}{A_1} + \ldots + \frac{1}{A_N}}$.

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}.

Constraints

• $1 \leq N \leq 100$
• $1 \leq A_i \leq 1000$

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.

见题面 Input 部分

见题面 Output 部分