You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance 1-(2-chlorophenyl)-4-methyl-7-(6-methylpyridazin-3-yl)-3,5-dihydro-2H-1,4-benzodiazepine .
user
C21H21ClN4
assistant