You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2-ethyl-4-phenylpiperazin-1-yl)-(3-methyl-2H-pyrazolo[3,4-b]pyridin-5-yl)methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H23N5O
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