You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (1S,2R,3aS,3bS,9aR,9bS,11aS)-1-[(1R)-1-hydroxyethyl]-2,9a,11a-trimethyl-1,2,3,3a,3b,4,6,8,9,9b,10,11-dodecahydroindeno[5,4-f]quinolin-7-one by IUPAC nomenclature, provide its molecular formula.
user
C21H33NO2
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