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(ls, val):
      i = 0
      while i < len(ls):
          if ls[i] == val:
              return i
          i = i + 1
      return -1
  
  
  def fibonacci(n):
      a = [0, 1, 1]
      i = 3
      while i < n:
          a.append(a[i - 1] + a[i - 2])
          i = i + 1
      return a[n]