You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 1-[3-(2,3-dichlorophenyl)sulfanylimidazo[1,5-a]pyrazin-8-yl]-4-methylpiperidin-4-amine by IUPAC nomenclature, provide its molecular formula.
user
C18H19Cl2N5S
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