TASK DEFINITION: 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".
PROBLEM: I saw him leaving the main building.

SOLUTION: acceptable

PROBLEM: To behave oneself in public is expected.

SOLUTION: acceptable

PROBLEM: the whistle tune was beautiful.

SOLUTION:
unacceptable