You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
6-bromo-N-butyl-13-chloro-N-ethyl-4-azatricyclo[9.4.0.03,8]pentadeca-1(11),3(8),4,6,12,14-hexaen-2-amine is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H24BrClN2
assistant