input: 
  def max_of_three(a, b, c):
      """ Find the maximum of three given numbers.
      >>> max_of_three(3, 4, 5)
      5
      >>> max_of_three(10, 5, 7)
      10
      >>> max_of_three(8, 9, 6)
      9
      """
  
output:     if a >= b and a >= c:
          return a
      elif b >= a and b >= c:
          return b
      else:
          return c