You're given a sentence and your task is to classify whether the sentence is acceptable or not. Any sentence which is grammatically correct, has a naturalistic text, is written by a native speaker and which minimizes superfluous content is acceptable, otherwise unacceptable. If the sentence is acceptable then write "acceptable", otherwise "unacceptable".

Example Input: Ellen conferred to Helen.
Example Output: unacceptable

Example Input: One of the problems was the robins.
Example Output: acceptable

Example Input: Who do you believe that invited Sara?
Example Output:
unacceptable