Initialize the Bank class with an array or map to store account balances.
For each transfer operation, check if both account numbers are valid and if the source account has enough balance. If valid, subtract the money from the source account and add it to the destination account.
For each deposit operation, check if the account number is valid. If valid, add the money to the account's balance.
For each withdraw operation, check if the account number is valid and if the account has enough balance. If valid, subtract the money from the account's balance.