You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (2R)-2-[(3-chlorophenyl)methyl-[2-[(4-chlorophenyl)methylsulfanyl]acetyl]amino]-N-methylpropanamide into its molecular formula.
user
C20H22Cl2N2O2S
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