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 3-[4-[(9-nitro-2,3,5,6-tetrahydroimidazo[2,1-b][1,3,6]oxadiazocin-4-yl)methyl]phenyl]benzonitrile .
user
C21H19N5O3
assistant