You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named ethyl (1R,6R)-4-(4-fluorophenyl)-6-(4-nitrophenyl)-2-oxocyclohex-3-ene-1-carboxylate by IUPAC nomenclature, provide its molecular formula.
user
C21H18FNO5
assistant