You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (5S)-1-[2-(4-chlorophenyl)ethyl]-5-[4-(2-methoxyethyl)piperazine-1-carbonyl]piperidin-2-one by IUPAC nomenclature, provide its molecular formula.
user
C21H30ClN3O3
assistant