You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(1R)-2,3-dihydro-1H-inden-1-yl]-1-(4-propan-2-ylpiperazin-1-yl)ethanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H26N2O
assistant