You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(1R)-6-fluoro-8-methylsulfonyl-2,3,4,9-tetrahydro-1H-carbazol-1-yl]butanoic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C17H20FNO4S
assistant