You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 1-(7-propan-2-ylspiro[6,8-dihydroimidazo[1,5-a]pyrazine-5,3'-piperidine]-1'-yl)-2-pyridin-2-ylethanone is given. What is its corresponding molecular formula?
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C20H27N5O
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