You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (11bS)-2-[[(1S)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl]methyl]-3-ethyl-4,6,7,11b-tetrahydro-1H-benzo[a]quinolizine into molecular formula.
user
C27H34N2O2
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