You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
15-fluoro-14-[3-(4-methylpiperazin-1-yl)propylamino]-18-oxo-12-oxa-1-azapentacyclo[11.7.1.02,11.05,10.017,21]henicosa-2(11),3,5,7,9,13(21),14,16,19-nonaene-19-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C28H27FN4O4
assistant