You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(4-nitrophenyl)-6-phenyl-4-(4-phenylmethoxyphenyl)-1,2,4,5-tetrazin-2-ium-3-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C27H20N5O4+
assistant