You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (1S,13S)-16,17-dimethoxy-2,6,20-trioxapentacyclo[11.8.0.03,11.05,9.014,19]henicosa-3(11),4,7,9,14,16,18-heptaen-12-one by IUPAC nomenclature, provide its molecular formula.
user
C20H16O6
assistant