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 ethyl 2-[(2S,3R,4S)-6-chloro-4-(1H-indol-3-yl)-3-nitro-3,4-dihydro-2H-chromen-2-yl]acetate is given. What is its corresponding molecular formula?
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C21H19ClN2O5
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