You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[2-(3,4-dihydro-2H-quinolin-1-yl)-2-oxoethyl]-7-phenylpyrazolo[3,4-d]triazin-4-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H18N6O2
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