using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Insert your grade: ");

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

        int avg = 0;

        int sum = 0;

        int ag = 1;

        while (ag == 1)

        {

            if (grade < 90 && grade > 50)

            {

            sum = sum + grade;

            avg++;

            }

            Console.WriteLine("Insert the number : 1 if you ant to insert the next grade...");

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

            if (ag==1)

            {

            Console.WriteLine("Insert your grade: ");

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

            }

        }

​

        Console.WriteLine(" the average grade is: {0}", (sum / avg));

    }

}