You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 1-[(3S)-3-(4-fluoro-N-methylanilino)-1-oxa-8-azaspiro[4.5]decan-8-yl]-2-methoxy-2-methylpropan-1-one into molecular formula.
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C20H29FN2O3
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