func_code: def countdown(num=3):
      while num != 0:
          print(num)
          num = num - 1
      print('LIFT OFF!')
  
  
  def search(ls, val):
      i = 0
      while i < len(ls):
          if ls[i] == val:
              return True
      i = i + 1
      return False
  
  
  def index(word, letter):
      if letter not in word:
          return -1
      else:
          i = 0
          while word[i] != letter:
              i = i + 1
          return i
  
  
  def fibonacci(n):
      import math
      Phi = 1.61803398875
      return int((Phi ** n - (1 - Phi) ** n) / math.sqrt(5))