You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(5S)-3-cyano-5-methyl-4,5,6,7-tetrahydro-1-benzothiophen-2-yl]-3-methoxybenzamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H18N2O2S
assistant