text: import sys
  
  
  def hello(name=None):
      if name is not None:
          return "Hello " + str(name) + "!"
      else:
          return "Hello world!"
  
  
  def main():
      print(hello())
  
      for arg in sys.argv[1:]:
          print(hello(arg))
  
  
  if __name__ == '__main__':
      main()
  