text: """
  Think Python, 2nd Edition
  Chapter 6
  Exercise 6.1
  
  Description: 
  
  Draw a stack diagram for the following program. What does the program print?
  
  def b(z):
      prod = a(z, z)
      print(z, prod)
      return prod
  
  def a(x, y):
      x = x + 1
      return x * y
  
  def c(x, y, z):
      total = x + y + z
      square = b(total)**2
      return square
  
  x = 1
  y = x + 1
  print(c(x, y+3, x+y))
  """
  
  # Stack diagram
  
  #   __main__    | x -> 1   y -> 2                                        |
  #   c           | x -> 1   y -> 5   z -> 3   total -> 9   square -> 8100 |
  #   b           | z -> 9   prod -> 90                                    |
  #   a           | x -> 10   y -> 9                                       |
  
  
  # Answer
  
  # What does the program print?
  #   The program print:
  #       9 90 in the first line
  #       8100 in the seconf line
  