You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[4-[[amino-[2-(ethenylamino)-5-nitro-6-oxo-1H-pyridin-3-yl]methylidene]amino]phenyl]-3,4-difluorobenzamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H16F2N6O4
assistant