Problem:
Score : 100 points

Problem Statement

Given is an integer N.

Takahashi chooses an integer a from the positive integers not greater than N with equal probability.

Find the probability that a is odd.

Constraints

1 \leq N \leq 100

Input

Input is given from Standard Input in the following format:

N

Output

Print the probability that a is odd.
Your output will be considered correct when its absolute or relative error from the judge's output is at most 10^{-6}.

Sample Input 1

4

Sample Output 1

0.5000000000

There are four positive integers not greater than 4: 1, 2, 3, and 4. Among them, we have two odd numbers: 1 and 3. Thus, the answer is \frac{2}{4} = 0.5.

Sample Input 2

5

Sample Output 2

0.6000000000

Sample Input 3

1

Sample Output 3

1.0000000000

Solution in Ruby (2.3.3) (judge verdict: Wrong Answer)

# n = gets.chomp.split.map(&:to_i)
# a = gets.to_f

# ans = 2 * n / a

# puts ans

# https://qiita.com/nasuka/items/21d7cd9acee9187c961e

n = gets.to_f

a = 0
count = 0

(1..n).each do a # each do で数を取り出す
  if a.odd?  # が奇数の時trueを返す→カウントを足す
    count += 1
  end
end
  
puts count / n.to_f 
  # to_f で小数点以下を表示