You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
14-phenyl-12,15-diazatetracyclo[8.7.0.02,7.011,15]heptadeca-1(10),2,4,6,8,11,13-heptaene is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H16N2
assistant