using System;

​

public class Program

{

    public static void Main()

    {

        int students = 1, count1 = 0, count2 = 0;

        while (students != 0)

        {

            Console.WriteLine("number of students: ");

            students = int.Parse(Console.ReadLine());

            while (students < 0)

            {

                Console.WriteLine("enter again");

                students = int.Parse(Console.ReadLine());

            }

​

            if (students > 41)

                count1++;

            if (students < 15 && students > 0)

                count2++;

        }

​

        Console.WriteLine("Number of classes over 41 students : " + count1);

        Console.WriteLine("Number of classes below 15 students: " + count2);

    }

}