You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
9-amino-2-cyclobutyl-5-(2,6-difluoropyridin-3-yl)-3H-pyrrolo[3,4-b]quinolin-1-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H16F2N4O
assistant