You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (1R,9R,13S)-11-methyl-1,9-dinitro-13-phenacyl-11-azatricyclo[7.3.1.02,7]trideca-2,4,6-trien-8-one into its molecular formula.
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C21H19N3O6
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