You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
9-[7-[4-[9,9-dimethyl-5-[[9-methyl-2-(4-methylnaphthalen-1-yl)fluoren-9-yl]methyl]fluoren-1-yl]naphthalen-1-yl]-4-methylnaphthalen-1-yl]-11,11-dimethylbenzo[a]fluorene is the IUPAC name of a molecule. Please give its molecular formula.
user
C81H62
assistant