You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-4-[(2S)-butan-2-yl]-8-(4-methoxyphenyl)sulfonyl-2-propan-2-yl-1,4,8-triazaspiro[4.5]decan-3-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H33N3O4S
assistant