You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name N-[2-[(8R)-2-butanoyl-5-oxa-2-azaspiro[3.4]octan-8-yl]ethyl]pyridine-4-carboxamide into its molecular formula.
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C18H25N3O3
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