using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var list = new List<string>

        {

            "U-70754, U-70755",

            "U-70754, U-70755",

            "U-70754, U-70755, U-70786, U-70787, U-70788",

            "U-70754, U-70755, U-70786, U-70787, U-70788",

            "U-70754, U-70755, U-70786, U-70787, U-70788",

            "U-70754, U-70755, U-70786, U-70787, U-70788"   

        };

        var filteredList = list.SelectMany(x => x.Split(",", StringSplitOptions.RemoveEmptyEntries))

                               .Select(x => x.Trim())

                               .Distinct()

                               .OrderBy(x => x);

        filteredList.ToList()

                    .ForEach(s => Console.WriteLine(s));

    }

}