You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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What is the molecular formula of the molecule identified by (6R,12aS)-9-amino-8-chloro-1,6,10,12,12a-pentahydroxy-6-methyl-3,11-dioxo-4,4a,5,5a,11a,12-hexahydrotetracene-2-carboxamide ?
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C20H21ClN2O8
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