You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4,6-dimethyl-2-(2-methylspiro[5,6-dihydrocyclopenta[d]pyrimidine-7,3'-piperidine]-1'-yl)pyridine-3-carbonitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H23N5
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