You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[[5-(azepan-1-yl)furan-2-yl]methylideneamino]-6-bromo-2-ethylquinazolin-4-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23BrN4O2
assistant