You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[[[(6aS,9R)-3-fluoro-12-oxo-6,6a,7,8,9,10-hexahydro-5H-pyrido[1,2-b][2]benzazepin-9-yl]-aminomethylidene]amino] 5-fluoropyridine-2-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H20F2N4O3
assistant