input: 
  from typing import List
  
  class MedianFinder:
      def __init__(self):
          self._data = []
      
      def add(self, num: int) -> None:
          self._data.append(num)
      
      def find_median(self) -> float:
          """ Find the median of the current list of numbers.
          >>> obj = MedianFinder()
          >>> obj.add(1)
          >>> obj.add(3)
          >>> obj.add(2)
          >>> obj.find_median()
          2.0
          >>> obj.add(5)
          >>> obj.add(4)
          >>> obj.find_median()
          3.0
          """
          data = sorted(self._data)
          n = len(data)
          return (data[(n-1)//2] + data[n//2]) / 2
  
output:     
          data = sorted(self._data)
          n = len(data)
          return (data[(n-1)//2] + data[n//2]) / 2
  