You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1R,4S,5R,8S,9R,12S,13R)-9-[(E)-but-2-enyl]-1,5-dimethyl-11,14,15,16-tetraoxatetracyclo[10.3.1.04,13.08,13]hexadecan-10-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H26O5
assistant