class BankAccount(object):

    def withdraw(self):
        pass

    def deposit(self):
        pass

class SavingsAccount(BankAccount):

    balance = float(0);

    def __init__(self):
        self.balance = 500

    def deposit(self, amount):
        if amount < 0:
            return "Invalid deposit amount"
        self.balance += amount
        return self.balance

    def withdraw(self, amount):
        if amount > self.balance:
            return "Cannot withdraw beyond the current account balance"
        if (self.balance-amount) < 500:
            return "Cannot withdraw beyond the minimum account balance"
        if amount < 0:
            return "Invalid withdraw amount"
        self.balance -= amount
        return self.balance

class CurrentAccount(BankAccount):

    balance = float(0);

    def __init__(self):
        balance = 0;

    def deposit(self, amount):
        if amount < 0:
            return "Invalid deposit amount"
        self.balance += amount
        return self.balance

    def withdraw(self, amount):
        if (self.balance-amount) < 0:
            return "Cannot withdraw beyond the current account balance"
        if amount < 0:
            return "Invalid deposit amount"
        self.balance -= amount
        return self.balance