You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-(4-methylsulfanylphenyl)-1-[2-(4-nitroanilino)-2-oxoethyl]pyridin-1-ium-3-carboxamide into its molecular formula.
user
C21H19N4O4S+
assistant