You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[1-(4-chlorobenzoyl)piperidin-4-yl]-[(3S,5S)-3,5-dimethylpiperidin-1-yl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H27ClN2O2
assistant