input: from typing import List
  
  def find_max_of_three(numbers: List[int]) -> int:
      """
      Find the maximum of three numbers in the given list.
      
      >>> find_max_of_three([3, 4, 5])
      5
      
      >>> find_max_of_three([10, 20, 15])
      20
      """
output:     if len(numbers) != 3:
          raise ValueError("The list must contain exactly three numbers.")
      return max(numbers)