You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (11bR)-1-tert-butyl-2,3,4,6,7,11b-hexahydro-1H-pyrazino[2,1-a]isoquinolin-9-amine;2-(trifluoromethyl)pyrazine .
user
C21H28F3N5
assistant