You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(5-ethylthiophen-2-yl)methyl]-1-(hydroxymethyl)-3,4-dihydro-1H-isoquinoline-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H22N2O2S
assistant