input: from typing import List
  
  
  class Sum:
      def __init__(self, x: int, y: int):
          self.x = x
          self.y = y
      
      def add(self) -> int:
          """Return the sum of two integers.
          >>> Sum(3, 5).add()
          8
          >>> Sum(0, 0).add()
          0
          >>> Sum(-3, 3).add()
          0
          """
          return self.x + self.y
output:     return self.x + self.y