You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (6S,9S)-6-(2,3-difluorophenyl)-9-prop-2-enyl-3-(2,2,2-trifluoroethyl)-6,7,8,9-tetrahydro-5H-imidazo[1,2-a]azepine by IUPAC nomenclature, provide its molecular formula.
user
C19H19F5N2
assistant