You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1S)-1-[(2S,3R,12bS)-2-(methylamino)-11-(3-methylphenyl)-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizin-3-yl]ethanol is the IUPAC name of a molecule. Please give its molecular formula.
user
C25H31N3O
assistant