You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
spiro[1,10,11,12,18,19-hexazatetracyclo[15.2.1.110,13.03,8]henicosa-3,5,7,11,13(21),17(20),18-heptaene-15,9'-fluorene] The above is the IUPAC name of a molecule. Write its molecular formula.
user
C27H22N6
assistant