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 (5aS)-6,6-dimethyl-2-nitro-5a-[(E)-2-(4-nitrophenyl)ethenyl]-12H-indolo[2,1-b][1,3]benzoxazine .
user
C25H21N3O5
assistant