You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[(3-cyano-6-methyl-5,6,7,8-tetrahydroquinolin-2-yl)sulfanyl]-N-(4-methoxyphenyl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23N3O2S
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