using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var input = "Hello world".ToCharArray();

        var vowels = "aeiouAEIOU".ToCharArray();

        input.Where(c=>vowels.Contains(c)).ToList().ForEach(v=>Console.WriteLine("[Server] Vowel characters deteced: " + v));   

    }

}