You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 3-[2-(3,4-dihydro-2H-quinolin-1-yl)-2-oxoethyl]-N-methyl-4-oxophthalazine-1-carboxamide into its molecular formula.
user
C21H20N4O3
assistant