You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 17-ethyl-14-methyl-15-phenyl-2,9,11-triaza-17-azoniatetracyclo[8.7.0.03,8.011,16]heptadeca-1(17),3,5,7,9,13,15-heptaene by IUPAC nomenclature, provide its molecular formula.
user
C22H21N4+
assistant