percentage of marks of more than one student

using System;
using System.Collections.Generic;
using System.Text;

using System.Collections.Specialized;
using System.Collections;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Hashtable ht = new Hashtable();

            int __english_max_marks = 100;
            int __maths_max_marks = 100;
            int __science_max_marks = 100;

            do
            {
                Console.WriteLine("");
                Console.Write("Enter Name Of Student : ");
                string studentName = Console.ReadLine();

                ArrayList al = new ArrayList();

                int[] ArrMarks = new int[3];

                Console.Write("Enter Marks Of English : ");
                int.TryParse(Console.ReadLine(), out ArrMarks[0]);
                Console.Write("Enter Marks Of Maths : ");
                int.TryParse(Console.ReadLine(), out ArrMarks[1]);
                Console.Write("Enter Marks Of Science : ");
                int.TryParse(Console.ReadLine(), out ArrMarks[2]);

                ht.Add(studentName, ArrMarks);

                Console.WriteLine("Would You Like To Read More Records ? Y/N");
            }
            while (Console.ReadKey().KeyChar.ToString().ToUpper() == "Y");

            Console.WriteLine("");
            Console.WriteLine("");

            foreach (string sk in ht.Keys)
            {
                int[] Arr = (int[])ht[sk];

                int all_marks = __english_max_marks + __maths_max_marks + __science_max_marks;

                float __percent = ((Arr[0] + Arr[1] + Arr[2]) * 100) / all_marks;

                Console.WriteLine(sk + " : " + __percent + " %");
            }

            Console.WriteLine("");
            Console.WriteLine("Press a key to Quit !");
            Console.ReadKey();
        }
    }
}