class Leaf:
    def __init__(self, value: int):
        self.value = value
    def __repr__(self):
        return f'Leaf({self.value})'

class Node:
    def __init__(self, left: 'Tree', right: 'Tree'):
        self.left = left
        self.right = right
    def __repr__(self):
        return f'Node({self.left}, {self.right})'

type Tree = Leaf | Node
# remove "type" from the previous line for Python 3.11, i.e., replace by
# Tree = Leaf | Node