You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(1R)-1-[[(2S,3R,11bS)-3-ethyl-9,10-dimethoxy-2,3,4,6,7,11b-hexahydro-1H-benzo[a]quinolizin-2-yl]methyl]-7-methoxy-1,2,3,4-tetrahydroisoquinolin-6-yl] ethyl carbonate is the IUPAC name of a molecule. Please give its molecular formula.
user
C31H42N2O6
assistant