You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named methyl 2,7,7-trimethyl-5-oxo-4-thiophen-2-yl-1,4,4a,6-tetrahydroquinoline-3-carboxylate is given. What is its corresponding molecular formula?
user
C18H21NO3S
assistant