You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(3S)-4-acetyl-3-methyl-2,3,4a,5,6,7,8,8a-octahydroquinoxalin-1-yl]-2-(4-chlorocyclohexyl)oxyethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H31ClN2O3
assistant