You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 4-[(4aR,9bR)-5-(4-fluorophenyl)-3,4,4a,9b-tetrahydro-1H-pyrido[4,3-b]indol-2-yl]-1-(4-fluorophenyl)butan-1-ol by IUPAC nomenclature, provide its molecular formula.
user
C27H28F2N2O
assistant