You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 1,2,6,7-tetramethyl-9H-fluorene;1,3,6,7-tetramethyl-9H-fluorene;1,4,6,7-tetramethyl-9H-fluorene;2,3,5,7-tetramethyl-9H-fluorene;2,3,6,7-tetramethyl-9H-fluorene .
user
C85H90
assistant