You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance (3aS,6R,6aS,9aR,10aS,10bR)-6a,9a-dichloro-6-(5-chloro-2-hydroxyphenyl)-8-methyl-3a,4,6,10,10a,10b-hexahydroisoindolo[5,6-e]isoindole-1,3,7,9-tetrone .
user
C21H17Cl3N2O5
assistant