You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 5-methyl-4-[(6-methyl-1-oxidopyridin-1-ium-3-yl)oxymethyl]thiophene-2-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C14H15NO4S
assistant