You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named methyl 6-methoxy-2-(2-methoxy-7-methylquinoxalin-5-yl)-1,3-benzothiazole-4-carboxylate by IUPAC nomenclature, provide its molecular formula.
user
C20H17N3O4S
assistant