You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the compound with this IUPAC name [(6aS,10aS)-5-chloro-7-methyl-6,6a,8,9,10,10a-hexahydro-4H-indolo[4,3-fg]quinolin-9-yl]methyl methyl carbonate ?
user
C18H21ClN2O3
assistant