You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 3a,6-dimethyl-6-(3-nitrosobutyl)-1,2,4,5,5a,7,8,9,9a,9b-decahydrocyclopenta[a]naphthalen-3-one into molecular formula.
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C19H31NO2
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