You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule ethyl (2R,3aS,9bR)-8-chloro-1-methyl-3,3a,4,9b-tetrahydro-2H-chromeno[4,3-b]pyrrole-2-carboxylate ?
user
C15H18ClNO3
assistant