You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule [4-(4-amino-1-methylpyrazolo[3,4-d]pyrimidin-6-yl)piperazin-1-yl]-(4-methylphenyl)methanone into molecular formula.
user
C18H21N7O
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