input: from typing import List
  
  
  def Strongest_Extension(class_name: str, extensions: List[str]) -> str:
      """You will be given the name of a class (a string) and a list of extensions.
      The extensions are to be used to load additional classes to the class. The
      strength of the extension is as follows: Let CAP be the number of the uppercase
      letters in the extension's name, and let SM be the number of lowercase letters 
      in the extension's name, the strength is given by the fraction CAP - SM. 
      You should find the strongest extension and return a string in this 
      format: ClassName.StrongestExtensionName.
      If there are two or more extensions with the same strength, you should
      choose the one that comes first in the list.
      Example:
      for Strongest_Extension('my_class', ['AA', 'Be', 'CC']) == 'my_class.AA'
      """
output:     max_strength = float('-inf')
      strongest_extension = ""
      
      for ext in extensions:
          CAP = sum(1 for c in ext if c.isupper())
          SM = sum(1 for c in ext if c.islower())
          strength = CAP - SM
          
          if strength > max_strength:
              max_strength = strength
              strongest_extension = ext
      
      return f"{class_name}.{strongest_extension}"