using System;
using System.Collections.Generic;

class MainClass
{
  public static void Main (string[] args)
  {
    Console.WriteLine ("Hello World");
  }

  public abstract class Order
  {
    public abstract List<Item> OrderItems { get; set; }
    public abstract decimal CaclulateOrderTotal();
  }

  public class Item
  {
    public int Quantity {get; set;}
  }

  public class ItemGram : Order
  {
    public override List<Item> OrderItems { get; set; }
    public override decimal CaclulateOrderTotal()
    {
      decimal total = 0;
        foreach (var item in OrderItems)
          total += item.Quantity * 6m / 1000;

      return total;
    }
  }

  public class ItemBottle : Order
  {
    public override List<Item> OrderItems { get; set; }
    public override decimal CaclulateOrderTotal()
    {
      decimal total = 0;
        foreach (var item in OrderItems)
          total += item.Quantity * 3m;

      return total;
    }
  }

  public class ItemBag : Order
  {
    public override List<Item> OrderItems { get; set; }
    public override decimal CaclulateOrderTotal()
    {
      decimal total = 0;
        foreach (var item in OrderItems)
          total += GetTotal(item);

      return total;
    }

    private decimal GetTotal(Item item)
    {
      var total = item.Quantity * .2m;
      int setsOfFour = item.Quantity / 4;
      total -= setsOfFour * .15m; //discount on groups of 4 items

      return total;
    }
  }

  public class Calculator
  {
    public decimal CalculateOrder(Order order)
    {
      return order.CaclulateOrderTotal();
    }
  }
}