using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var items = new string[]

        {

            "System",

            "System.Collection.Generic",

            "System.Generic",

            "System.Linq",

            "System.Linq.Collection.Generic"

        };

        var sortedItems = items

            // Order by number of periods ("levels")

            .OrderBy(x => x.Count(c => c == '.'))

            // Then everything else alphabetically

            .ThenBy(x => x);

        foreach (var item in sortedItems)

        {

            Console.WriteLine(item);

        }

    }

}