You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-(5-chloro-2-methylphenyl)-N-[1-(2-methylpropyl)piperidin-4-yl]piperazine-1-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H33ClN4O
assistant