You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-(4-chlorophenyl)-1-[2-(4-pyridin-2-ylpiperazine-1-carbonyl)-6-azaspiro[2.5]octan-6-yl]ethanone by IUPAC nomenclature, provide its molecular formula.
user
C25H29ClN4O2
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