using System;

using System.Collections.Generic;                   

public class Program

{

    public static void Main()

    {

        string s = "aeiou";

        List<char> sVowels = new List<char>();

        List<int> vowelPos = new List<int>();

        char[] vowels = {'a','e','i','o','u'};

        foreach(char x in s)

        {

            foreach(char y in vowels)

            {

                if (x == y)

                {

                    sVowels.Add(x);

                    vowelPos.Add(s.IndexOf(x));

                }

            }

        }

        sVowels.Reverse();

        List<char> answer = new List<char>();

        for(int i = 0; i==s.Length-1; i++)

        {

            if(vowelPos.Contains(s[i]))

               {

                    answer.Add

               }

        }

        foreach(char x in answer) 

        {

            Console.WriteLine(x);   

        }

    }

}