using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var school = new Dictionary<int, string[]> {

            [6] = new string[] { "Amy", "Charlie", "Daron" },

            [7] = new string[] { "Raul", "Jun", "Chris" },

            [8] = new string[] { "Yvonne", "Theo", "Carla" }            

        };

        IEnumerable<string> AllStudents() 

        {

            foreach ( var (grade, students) in school) 

            {

                foreach (var student in students)

                {

                    yield return student;   

                }

            }               

        };

        foreach (var student in AllStudents()) 

        {

            Console.WriteLine(student); 

        }

    }

}