You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-(2-methoxyphenyl)-3-(4-methylphenyl)sulfonyl-6,7-dihydro-4H-thieno[3,2-b]pyridin-5-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H19NO4S2
assistant