using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MarksAvgCalculator
{
    class Program
    {
        static void Main(string[] args)
        {
            double marksTotal = 0;
            int i = 0;
            string exit = "no";
            while (exit != "true")
            {
                i++;
                Console.WriteLine("Please enter mark:");
                double mark = double.Parse(Console.ReadLine());
                marksTotal += mark;
                Console.WriteLine("Would you like to insert another mark?");
                Console.WriteLine("y/n");
                string yN = Console.ReadLine();
                if (yN == "y")
                    Console.WriteLine();
                else if (yN == "n")
                {
                    Console.WriteLine();
                    exit = "true";
                }
                else
                    Console.WriteLine("Invalid choice.");
                Console.WriteLine();
            }
            Console.WriteLine("grades average is " + marksTotal / i);
        }
    }
}