You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(E)-3-[4-(difluoromethoxy)phenyl]-N-[3-fluoro-4-(2-oxopyrrolidin-1-yl)phenyl]prop-2-enamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H17F3N2O3
assistant