You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[2-[6-amino-8-[(6-bromo-1,3-benzodioxol-5-yl)sulfanyl]purin-9-yl]ethyl]piperidine-1-carboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H21BrN6O4S
assistant