You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Can you give the molecular formula of the molecule 1-methylidene-4-[1-(oxolan-3-yl)azetidin-3-yl]-3,5-dihydro-2H-indol-1-ium-5,7a-diide ?
user
C16H21N2O-
assistant