You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (7R)-N,7-dimethyl-N-(1-methylpiperidin-1-ium-4-yl)-5,6,7,8-tetrahydro-[1]benzothiolo[2,3-d]pyrimidin-4-amine into its molecular formula.
user
C18H27N4S+
assistant