You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2S,3S)-N-[(4-fluorophenyl)methyl]-1-methyl-6-oxo-2-thiophen-2-ylpiperidine-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H19FN2O2S
assistant