You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-butyl-7-[2-[3-fluoro-4-(trifluoromethoxy)phenyl]ethynyl]-1,2,3,4,4a,9,10,10a-octahydrophenanthrene is the IUPAC name of a molecule. Please give its molecular formula.
user
C27H28F4O
assistant