You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named N-[(3S,7R,8aS)-3-(2-hydroxyethyl)-3,4,6,7,8,8a-hexahydro-1H-pyrrolo[2,1-c][1,4]oxazin-7-yl]-2-(3-methylphenyl)acetamide by IUPAC nomenclature, provide its molecular formula.
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C18H26N2O3
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