You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4S)-3-amino-2-cyano-4-(furan-2-yl)-N-(2-methoxyphenyl)-6-methyl-4,7-dihydrothieno[2,3-b]pyridine-5-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18N4O3S
assistant