You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
tert-butyl N-[1-[4-(4-methoxyphenyl)piperazin-1-yl]-3-methyl-1-oxobutan-2-yl]carbamate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H33N3O4
assistant