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 architects haven't built a mill before year 1850? | architect : id , name , nationality , gender | bridge : architect_id , id , name , location , length_meters , length_feet | mill : architect_id , id , location , name , type , built_year , notes | bridge.architect_id = architect.id | mill.architect_id = architect.id | 

### Response:

select count ( _ ) from _ where _ not in ( select _ from _ where _ ) | select count ( * ) from architect where id not in ( select architect_id from mill where built_year < 1850 )