You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-bromo-6-[[4-hydroxy-3-(6-methyl-1H-benzimidazol-2-yl)phenyl]iminomethyl]-4-nitrophenol by IUPAC nomenclature, provide its molecular formula.
user
C21H15BrN4O4
assistant