You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 3-(4-chloroindol-1-yl)-N-[(2S)-1-hydroxy-4-methylsulfanylbutan-2-yl]propanamide by IUPAC nomenclature, provide its molecular formula.
user
C16H21ClN2O2S
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