You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3-hydroxy-7,14-dimethoxy-17-methyl-5-oxo-12,16,21-trioxapentacyclo[15.3.1.02,15.04,13.06,11]henicosa-2(15),3,6(11),7,9,13-hexaen-8-yl) hydrogen sulfate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20O11S
assistant