You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[4-(5-bromo-1H-indole-2-carbonyl)piperazin-1-yl]-(3,4-difluorophenyl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H16BrF2N3O2
assistant