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".

John looked up the meaning of ` chanson '.
acceptable

He established his innocence with the letter.
acceptable

John bought the picture of himself that Bill saw.

acceptable