You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
17-fluoro-5,7,14-trioxapentacyclo[11.8.0.03,11.04,8.015,20]henicosa-1(13),2,4(8),9,11,15(20),16,18-octaen-21-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H9FO4
assistant