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 (2S)-3-(cyclopropanecarbonyl)-1'-[(3,4-difluorophenyl)methyl]spiro[1,3-thiazolidine-2,3'-indole]-2'-one ?
user
C21H18F2N2O2S
assistant