You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named (3R,6R)-3-[(1R)-1-(5-chloro-1-ethylindol-3-yl)ethyl]-6-(1,3-thiazol-4-ylmethyl)piperazine-2,5-dione is given. What is its corresponding molecular formula?
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C20H21ClN4O2S
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