You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named [2-[(E)-(3-oxo-1-benzothiophen-2-ylidene)methyl]phenyl] 2-chloropyridine-3-carboxylate is given. What is its corresponding molecular formula?
user
C21H12ClNO3S
assistant