You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
9-[diphenyl-(6-propan-2-yl-1H-inden-1-yl)methyl]-2-N,7-N-dimethyl-9H-fluorene-2,7-diamine is the IUPAC name of a molecule. Please give its molecular formula.
user
C40H38N2
assistant