using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var source = new string[] {"A","B","C","111","11","123","1","42","5"};

        var sorted = source.OrderBy(x => x, new Comparer());

        Console.WriteLine(string.Join("\n", sorted));

    }

    public class Comparer : IComparer<string>

    {

        public int Compare(string a, string b) 

        {

            int ia = 0;

            int ib = 0;

            var aIsInt = int.TryParse(a,out ia);

            var bIsInt = int.TryParse(b,out ib);

            if (aIsInt == bIsInt)

            {

                if (aIsInt)

                {

                    return ia.CompareTo(ib);

                }

                else

                {

                    return a.CompareTo(b);

                }

            }

            return aIsInt ? -1 : 1;

        }

    }

}