You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (10bS)-9-bromo-1'-methylsulfonyl-2-pyridin-4-ylspiro[1,10b-dihydropyrazolo[1,5-c][1,3]benzoxazine-5,4'-piperidine] .
user
C20H21BrN4O3S
assistant