You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (1S)-1-ethyl-12-methyl-10-(3-methylbut-2-enyl)-10-azatricyclo[7.3.1.02,7]trideca-2(7),3,5-trien-4-ol by IUPAC nomenclature, provide its molecular formula.
user
C20H29NO
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