You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (1S,2S)-2-[[4-(1-pyridin-2-ylethylsulfanyl)phenyl]sulfonylmethyl]cyclohexane-1-carboxylic acid into its molecular formula.
user
C21H25NO4S2
assistant