You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-fluoro-4-(5,5,7,7-tetradeuterio-6-propyl-1,2,3,4,4a,6,8,8a-octahydronaphthalen-2-yl)benzonitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H26FN
assistant