You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-(7,8-dihydro-6H-[1,4]dioxepino[2,3-f]benzimidazol-3-yl)-N-(2,5-dimethylphenyl)acetamide into molecular formula.
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C20H21N3O3
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