You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(13R)-6-chloro-7,9,15-trihydroxy-13-methyl-12,19-dioxatricyclo[14.2.1.05,10]nonadeca-5(10),6,8,17-tetraene-3,11-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H19ClO7
assistant