using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

    public class NavBarItem

    {

        public int? Id { get; set; }

        public int? ParentId { get; set; }

        public string Name{get;set;}

        public IEnumerable<NavBarItem> Children { get; set; }

        public int ChildCount { get; set; }

        public int HierarchyLevel { get; set; }

        public int GetChildCount() => Children?.Sum(c => 1 + c.GetChildCount()) ?? 0;

    }

}