You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (1S,13S)-14,15-dimethoxy-20-methyl-5,7-dioxa-20-azapentacyclo[11.4.3.01,13.02,10.04,8]icosa-2,4(8),9,11,14-pentaen-16-one into molecular formula.
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C20H21NO5
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