You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1S,2R,3R,4S)-3-[4-(4-acetylphenyl)piperazine-1-carbonyl]bicyclo[2.2.1]heptane-2-carboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H26N2O4
assistant