You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (1S,4R,9S,10S,13R,16R,18R,19R)-18-hydroxy-5,5,9-trimethyl-15,17-dioxapentacyclo[11.5.1.01,10.04,9.016,19]nonadecan-14-one .
user
C20H30O4
assistant