using System;

​

public class Program

{

    public static void Main()

    {

        int num, hours;

        Console.WriteLine("enter number of hours");

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

        num=0;

        while(hours<70)

        {

            if(hours>=15)

                num=num+1;

         Console.WriteLine("enter number of hours");

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

        }

        Console.WriteLine(num+"numbers of students which dedicated more than 15 hours and less than 70 hours for H.W");

    }

}