You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(1R,2S,7R,11S)-4,9-dichloro-2-(hydroxymethyl)-4,9-diphenyl-3,5,8,10-tetraoxabicyclo[5.3.1]undecan-11-ol is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20Cl2O6
assistant