using System;

public class Program

{

    public static void Main()

    {

        var node = new Node(0);

        node.Left = new Node(1);

        node.Left.Parent = node;

        node.Right = new Node(2);

        node.Right.Parent = node;

        node.Left.Left = new Node(1);

        node.Left.Left.Parent = node.Left;

        node.Left.Right = new Node(2);

        node.Left.Right.Parent = node.Left;

        node.Right.Left = new Node(1);

        node.Right.Left.Parent = node.Right;

        node.Right.Right = new Node(3);

        node.Right.Right.Parent = node.Right;

        Console.WriteLine(LongestConsecutiveBranch(node));

    }

    public class Node

    {

        public int Data;

        public Node Left;

        public Node Right;

        public Node Parent;

        public Node(int data)

        {

            Data = data;

            Left = null;

            Right = null;

            Parent = null;

        }

    }

​

    public static int LongestConsecutiveBranch(Node node)

    {

        var length = 0;

        return PostOrder(node) + 1;

    }

​

    public static int PostOrder(Node node)

    {

        if (node == null)

            return 0;

​

        var left = PostOrder(node.Left);

        var right = PostOrder(node.Right);

        Console.WriteLine(node.Data);

​

        if (node.Parent != null && node.Data - 1 == node.Parent.Data)

        {

            Console.WriteLine("Return 1");  

            return 1;

        }

        return 0;

    }

​

}