You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-(4-bromo-3-methylpyrazol-1-yl)-N-[3-(4-chloro-2-methylphenoxy)-5-nitrophenyl]propanamide by IUPAC nomenclature, provide its molecular formula.
user
C20H18BrClN4O4
assistant