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 Ruby (2.3.3) (judge verdict: Accepted)

n = gets.to_i
a = gets.split.map(&:to_i)
inv = 0
b = 100000000
a.each do |num|
    inv += b/num
end
puts (b*b/inv)/b.to_f

=begin
n,m = gets.split.map(&:to_i)
puts ">"*(m*7+3)+"<<<<<<<[#{">"*(n*7)}+#{"<"*(n*7)}-]"*m+">"*(n*7-3)+"+"*n+"[-[<<<<<<<+>>>>>>>-]<<<<"+">>>>>>>[<<<<<<<+>>>>>>>-]"*m+"<"*(m*7+2)+"+[>+>"+"[>+>>+<<<-]>>>[<<<+>>>-]<<[->[>>+<]>[<]>-[>>>>+<<<<<<++++++++++>>+]<<-<]>>>>>>"*(m+1)+">["+"<"*(m*7+10)+"->->"+"[>+>>+<<<-]>>>[<<<+>>>-]<<[->---------[>>+<]>[<]>-[>>>>+<<<<<<---------->>+]<<++++++++++<]>>>>>>"*(m+1)+">[-]]"+"<"*(m*7+10)+"]<]"


# a/b
# n = ceil(log_10 a)
# m = ceil(log_10 b)
# 
# a = a_0+a_1*10+......a_(n-1)*10**(n-1)
# b = b_0+b_1*10+......b_(n-1)*10**(m-1)
#
# 7 cells = 1 digit
# [*][][][b_0][][a_0][] [][][][b_1][][a_1][] ......
# 
# [*][][quo_0][][][rem_0][] [][][quo_1][][][rem_1][] ......

=end