using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter the amount of hours you spend on doing homework");

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

        int students = 0;

        while (hours >= 15 && hours<=70)

        {   students++;

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

        }

        Console.WriteLine ("{0} students spend at least 15 hours on homework", students);

    }

}