using System;

// static type "interface" for bank account objects:
interface account
{
  int inquiry();
  void withdraw(int x);
  void deposit(int x);
}

// definition of superclass  "generic account"
class genaccount
{
   protected int balance;
   public int inquiry() { return balance; }
   public virtual void withdraw(int amt) // virtual means overridable
     { balance -= amt; }                 // function
   public virtual void deposit(int amt)
     { balance += amt; }
   public genaccount(int b) { balance = b; }
}

// subclasses:

// in Java, the following line would read
//   "class checking extends genaccount implements account
class checking : genaccount, account
{
   private int fee;
   public checking(int b, int f) : base(b)  // calls base class constructor
   {
      fee = f;
   }
   
   public override void withdraw(int amt)
   {
     balance = balance - amt - fee;
   }
}

class savings : genaccount, account
{
   private int bonus;
   public savings(int bl, int bn) : base(bl)
   {
     bonus = bn;
   }
   public override void deposit(int amt)
   { balance = balance + amt + bonus; }
}


public class objects2
{
   public static void Main(string[] args)
   {
     account a1, a2;    // note the static type
     a1 = new savings(500,2);  // note the dynamic type
     a2 = new checking(500,3);
     a1.deposit(200);
     a2.deposit(200);
     a1.withdraw(100);
     a2.withdraw(100);
     Console.WriteLine("a1's balance is "+a1.inquiry());
     Console.WriteLine("a2's balance is "+a2.inquiry());
   }
}