class Node:
    def __init__(self ,key):
        self.key = key
        self.child = []


def longestUnivaluePath(root):
    def arrow_length(node):
        global ans

        child_lengths = [ arrow_length(child_node)  for child_node in node.child ]
        child_arrows = [ (child_length+1) for child_node, child_length in zip(node.child, child_lengths) if child_node.key == node.key ]
        ans = max(child_arrows + [ans])

        return max(child_arrows) if child_arrows else 0

    arrow_length(root)
    return ans




root = Node(2)
child_nodes = [Node(2), Node(1), Node(10), Node(3)]
root.child = child_nodes

sub_child_nodes_2 = [Node(2), Node(2)]
child_nodes[0].child = sub_child_nodes_2

sub_child_nodes_1 = [Node(2), Node(3)]
child_nodes[1].child = sub_child_nodes_1

sub_child_nodes_10 = [Node(2), Node(3)]
child_nodes[2].child = sub_child_nodes_10

sub_child_nodes_3 = [Node(2), Node(3)]
child_nodes[3].child = sub_child_nodes_3

ans = 0
print longestUnivaluePath(root)