You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (7R,8aS)-7-(5-cyclopropylpyrazin-2-yl)oxy-2-(2,3-dichlorophenyl)sulfonyl-3,4,6,7,8,8a-hexahydro-1H-pyrrolo[1,2-a]pyrazine into its molecular formula.
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C20H22Cl2N4O3S
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