You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-(1,3-dioxo-6,7,8,8a-tetrahydro-5H-imidazo[1,5-a]pyridin-4-ium-4-yl)-5-fluoro-2-(furan-2-ylmethylsulfanyl)benzonitrile The above is the IUPAC name of a molecule. Write its molecular formula.
user
C19H17FN3O3S+
assistant