#!/usr/bin/env python
import typing


class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.right = right
        self.left = left


class Solution:
    def amountOfTime(self, root: typing.Optional[TreeNode], start: int) -> int:
        def dfs(node):
            if node is None:
                return
            if node.left:
                graph[node.val].append(node.left.val)
                graph[node.left.val].append(node.val)
            if node.right:
                graph[node.val].append(node.right.val)
                graph[node.right.val].append(node.val)
            dfs(node.left)
            dfs(node.right)

        graph = defaultdict(list)
        dfs(root)
        visited = set()
        queue = deque([start])
        time = -1
        while queue:
            time += 1
            for _ in range(len(queue)):
                current_node = queue.popleft()
                visited.add(current_node)
                for neighbor in graph[current_node]:
                    if neighbor not in visited:
                        queue.append(neighbor)
        return time


def main() -> None:
    pass


if __name__ == "__main__":
    main()