using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace ExamPreparation
{
    class Program
    {
        static void Main()
        {
            List<Student> oldStudents = new List<Student> { new Student(44, "Ivan Petrov"), new Student(34, "Milen Andonov"), new Student(55, "Dancho Bogdanov"), new Student(34, "Strahil Pavlov") };

            IEnumerable<GroupedStudents> groupedStudentsByAge = oldStudents
                .GroupBy(s => s.Age)
                .OrderByDescending(g => g.Key)
                .Select(g => new GroupedStudents
                {
                    Age = g.Key,
                    Count = g.Count(),
                    Students = g
                });

            PrintGroupedStudent(groupedStudentsByAge);
        }

        public static void PrintGroupedStudent(IEnumerable<GroupedStudents> groupedStudents )
        {
            foreach (var item in groupedStudents)
            {
                Console.WriteLine("There are {0} students at the age of {1}", item.Count, item.Age);
                foreach (var student in item.Students)
                {
                    Console.WriteLine(student.Name);
                }
            }
        }

        public class GroupedStudents
        {
            public int Age { get; set; }

            public int Count { get; set; }

            public IGrouping<int, Student> Students { get; set; }
        }


    public class Student
    {
        public Student(int age = 16, string name = "")
        {
            this.Age = age;
            this.Name = name;
        }

        public int Age { get; set; }
        public string Name { get; set; }
}