output_description: 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}.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: def ri():
      return int(input())
  
  
  def rli():
      return list(map(int, input().split()))
  
  
  def rls():
      return list(map(str, input().split()))
  
  
  def pl(a):
      print(" ".join(list(map(str, a))))
  
  
  def ma():
      return map(int, input().split())
  
  
  def nli(x):
      return [input for _ in range(x)]
  
  
  def hukusuu():
      listA = []  # appendのために宣言が必要
      while True:
          try:
              listA.append(list(map(int, input().split())))
          except:
              break  # または、quit(),os.exit()をして止める。
      return listA
  
  
  n = ri()
  if n % 2 == 0:
      print(0.5)
  else:
      print(((n // 2) + 1) / n)
  
problem_description: 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.
samples: [{"input": "4", "output": "0.5000000000\n    \n\nThere are four positive integers not greater than 4: 1, 2, 3, and 4. Among\nthem, we have two odd numbers: 1 and 3. Thus, the answer is \\frac{2}{4} = 0.5.\n\n* * *"}, {"input": "5", "output": "0.6000000000\n    \n\n* * *"}, {"input": "1", "output": "1.0000000000"}]