using System;

namespace Banking
{
    public class Account
    {
        private static int _nextAccountNumber;

        private int _accountNumber;
        private double _balance;

        public Account()
        {
          _accountNumber=_nextAccountNumber;
          _nextAccountNumber++;
        }

         public int AccountNumber 
         {
             get { return _accountNumber; }
         }

         public double Balance 
         {
             get { return _balance; }
             set { _balance=value; }
         }

        public static void Main(string[] args)
        {
            // Current Account #0
            CurrentAccount currentAccount=new CurrentAccount();
            currentAccount.Balance=100;
            System.Console.WriteLine("Current Account "+currentAccount.AccountNumber
              +" has balance "+currentAccount.Balance);

            // Current Account #1
            currentAccount=new CurrentAccount();
            currentAccount.Balance=100;
            currentAccount.directdebit(50);
            System.Console.WriteLine("Current Account "+currentAccount.AccountNumber
              +" has balance "+currentAccount.Balance);

            // Savings Account #1
            SavingsAccount savingsAccount=new SavingsAccount();
            savingsAccount.Balance=1000;
            savingsAccount.applyInterest(1.1);
            System.Console.WriteLine("Savings Account "+savingsAccount.AccountNumber
              +" has balance "+savingsAccount.Balance);

        }

    }

    public class CurrentAccount : Account
    {
        private SavingsAccount _surplusAccount;

        public double directdebit(double amount)
        {
            Balance=Balance-amount;
            return Balance;
        }
    }

    public class SavingsAccount : Account
    {
        public double applyInterest(double rate)
        {
            Balance=Balance*rate;
            return Balance;
        }
    }

}