You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the compound with this IUPAC name ethyl (4S)-2-amino-1-(5-bromopyridin-2-yl)-5-oxo-4-thiophen-2-yl-4,6,7,8-tetrahydroquinoline-3-carboxylate ?
user
C21H20BrN3O3S
assistant