You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 2-[[2-(5-chloro-1-methylbenzimidazol-2-yl)sulfanylacetyl]amino]-N-(2-ethylphenyl)acetamide into its molecular formula.
user
C20H21ClN4O2S
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