using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var thelist = new[] {"1", "item", "10", "2", "3", "4", "5", "a", "b", "c"};

        var list = thelist.Where( s => s.All( x => char.IsDigit( x ) ) )

                  .OrderBy( r => { int z; int.TryParse( r, out z ); return z; } )

                  .Union( thelist.Where( m => m.All( x => !char.IsDigit( x ) ) )

                               .OrderBy( q => q ) );

         foreach (var i in list)

            {

                Console.WriteLine(i.ToString());

            }

    }

}