You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 6-(4-acetylpiperazin-1-yl)-3,3,8-trimethyl-1,4-dihydropyrano[3,4-c]pyridin-7-ium-5-carbonitrile into its molecular formula.
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C18H25N4O2+
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