Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:

Convert text to sql: How many customers do not have an account? | accounts : account_id , customer_id , account_name , other_account_details | customers : customer_id , customer_first_name , customer_last_name , customer_address , customer_phone , customer_email , other_customer_details | customers_cards : card_id , customer_id , card_type_code , card_number , date_valid_from , date_valid_to , other_card_details | financial_transactions : transaction_id , previous_transaction_id , account_id , card_id , transaction_type , transaction_date , transaction_amount , transaction_comment , other_transaction_details | financial_transactions.account_id = accounts.account_id | financial_transactions.card_id = customers_cards.card_id | 

### Response:

select count ( _ ) from _ where _ not in ( select _ from _ ) | select count ( * ) from customers where customer_id not in ( select customer_id from accounts )