You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2S)-N-[(4-bromo-3-nitrophenyl)methylideneamino]-3-methyl-2-[[2-(3-methylphenoxy)acetyl]amino]butanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23BrN4O5
assistant