def retrieveTree(self, coordinate, level):
  if not level % 2:
    # genap
    if coordinate[0] < self.coordinate[0]:
      # kiri
      if not hasattr(self, 'left'):
        return self.coordinate
      return self.left.retrieveTree(coordinate, level+1)
    elif coordinate[0] > self.coordinate[0]:
      # kanan
      if not hasattr(self, 'right'):
        return self.coordinate
      return self.right.retrieveTree(coordinate, level+1)
    else:
      # sama
      return self.coordinate
  else:
    # ganjil
    if coordinate[1] < self.coordinate[1]:
      # kiri
      if not hasattr(self, 'left'):
        return self.coordinate
      return self.left.retrieveTree(coordinate, level+1)
    elif coordinate[1] > self.coordinate[1]:
      # kanan
      if not hasattr(self, 'right'):
        return self.coordinate
      return self.right.retrieveTree(coordinate, level+1)
    else:
      # sama
      return self.coordinate