class TreeNode:
    def __init__(self, value, parent=None):
        self.value = value
        self.parent = parent
        self.children = []

    def add_child(self, child_node):
        child_node.parent = self
        self.children.append(child_node)

    def remove_child(self, child_node):
        self.children = [child for child in self.children if child is not child_node]
        child_node.parent = None

    def __repr__(self, level=0):
        ret = "\t" * level + repr(self.value) + "\n"
        for child in self.children:
            ret += child.__repr__(level + 1)
        return ret

    def get_ancestors(self):
        """返回当前节点及其所有祖先节点"""
        ancestors = []
        node = self
        ancestors.append(node)
        while node.parent:
            ancestors.append(node.parent)
            node = node.parent
        return ancestors

class Tree:
    def __init__(self, root_value):
        self.root = TreeNode(root_value)

    def add_child(self, parent_node, child_value):
        if not parent_node:
            parent_node = self.root
        parent_node.add_child(TreeNode(child_value))

    def find(self, value):
        return self._find_in_node(self.root, value)

    def _find_in_node(self, node, value):
        if node.value == value:
            return node
        for child in node.children:
            found_node = self._find_in_node(child, value)
            if found_node:
                return found_node
        return None

    def __repr__(self):
        return repr(self.root)