using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.IO;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

​

​

        private IEnumerable<IEnumerable<T>> GetAllEnumerators<T>(IEnumerable<T> parent)

        {

            var result = new List<IEnumerable<T>>();

​

            var stack = new Stack<IEnumerable<T>>();

            stack.Push(parent);

​

            while (stack.Count > 0)

            {

                var current = stack.Pop();

                if (current != null)

                {

                    result.Add(current);

​

                    if (current.GetEnumerator() != null)

                    {

                        foreach (var child in current)

                        {

                            stack.Push(child as IEnumerable<T>);

                        }

                    }

                }

            }

​

            return result;

        }

}