new_contents: """The tower of Hanoi."""
  from __future__ import print_function
  
  def move_towers(height, from_pole, to_pole, with_pole):
      move_towers(height - 1, from_pole, with_pole, to_pole)
      move_disk(from_pole, to_pole)
      move_towers(height - 1, with_pole, to_pole, from_pole)
  
  
  def move_disk(from_pole, to_pole):
      print('Moving disk from {0} to {1}'
            .format(from_pole, to_pole))
  
subject: Complete alg: tower of hanoi