You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
tert-butyl 4-[2-[(2S)-2-tert-butyl-4-methylpiperazin-1-yl]-2-oxoethyl]piperidine-1-carboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H39N3O3
assistant