You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (3aS,6aR)-2-[2-(3-phenylcyclobutyl)acetyl]-1,3,4,5,6,6a-hexahydrocyclopenta[c]pyrrole-3a-carboxylic acid by IUPAC nomenclature, provide its molecular formula.
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C20H25NO3
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