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 2-[(4aS,7aR)-3,4a,5,6,7,7a-hexahydro-2H-cyclopenta[b][1,4]oxazin-4-yl]-1-[4-(thiophen-3-ylmethyl)piperazin-1-yl]ethanone .
user
C18H27N3O2S
assistant