using System;

public class Program

{

    public static bool avg (int num1,int num2,int num3)

    {

        if ((num1+num2+num3)/3>80)

            return true;

        else

            return false;

    }

}       

    public static void main()

        {

                int num1,num2,num3,i;

                i = 0;

                while(i<=10)

                {

                    Console.WriteLine("enter 3 grades");

                    num1=int.Parse(Console.ReadLine());

                    num2=int.Parse(Console.ReadLine());

                    num3=int.Parse(Console.ReadLine());

                    if(avg(num1,num2,num3)==true)

                    {

                        Console.WriteLine("yes");

                    }

                    else

                    {Console.WriteLine("no");

                    }

                }

            }

​

​

​