You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(7-nitro-5-pyridin-2-yl-3H-1,4-benzodiazepin-2-yl)amino] N-(3-chlorophenyl)carbamate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H15ClN6O4
assistant