You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named methyl 2-[5-chloro-4-[(3-ethyl-1-methylpyrazol-4-yl)methylamino]-6-oxopyridazin-1-yl]benzoate by IUPAC nomenclature, provide its molecular formula.
user
C19H20ClN5O3
assistant