You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-methyl-6-(1-methyl-5-phenylpyridin-1-ium-2-yl)-9,9-bis(trideuteriomethyl)indeno[2,1-b]pyridine is the IUPAC name of a molecule. Please give its molecular formula.
user
C27H25N2+
assistant