You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(9S)-2-methyl-9-phenyl-6,7,8,9-tetrahydro-5H-imidazo[1,2-a][1,4]diazepine is the IUPAC name of a molecule. Please give its molecular formula.
user
C14H17N3
assistant