using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static string ReverseWords(string strs)

    {

        string [] words = strs.Split(' ');

        Array.Reverse(words);

        return string.Join(" ", words);

    }

  public static string HighAndLow(string numbers)

  {

​

  }

    public static IEnumerable<string> FriendOrFoe (string[] names) {

    return names.Where(u=>u.Length==4);

    }

​

    public static void Main()

    {

        string str = "Hello World";

        string[] names = { "Ryan", "Kieran", "Mark", "Jimmy" };

        IEnumerable<string> friends = FriendOrFoe(names);

        foreach(var n in friends)

        {

            Console.WriteLine(n);

        }

        Console.WriteLine(HighAndLow("5 3 5 1 7 -9 3 8 3 1 4 7 8 5 2 9 6 3"));

        Console.WriteLine(str.IndexOf("ld"));

        Console.WriteLine(ReverseWords(str));

    }

}

​

​