old_contents: def square_of_sum():
      pass
  
  
  def sum_of_squares():
      pass
  
  
  def difference():
      pass
  
new_contents: def square_of_sum(n):
      return square(sum(range(n+1)))
  
  
  def sum_of_squares(n):
      return sum(map(square, range(n+1)))
  
  
  def difference(n):
      return square_of_sum(n) - sum_of_squares(n)
  
  
  def square(n):
      return n*n
  
subject: Add initial solution