You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(5-chlorothiophen-2-yl)methyl]-N-ethyl-1-(3-methoxyphenyl)-5-oxopyrrolidine-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H21ClN2O3S
assistant