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".

[Q]: Bill understands Mary and himself.
[A]: unacceptable


[Q]: Cynthia ate the peach with a fork.
[A]: acceptable


[Q]: It is difficult for me to concentrate on calculus.
[A]:
acceptable