You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(12E,15S)-18-chloro-5,15-bis(methylamino)-8,17,19-triazatricyclo[14.2.1.02,7]nonadeca-1(18),2(7),3,5,12,16(19)-hexaen-9-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H22ClN5O
assistant