You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 2-[[(1R)-1-(3-bromo-4-methoxyphenyl)ethyl]amino]-N-(5-chloro-2-methylphenyl)acetamide by IUPAC nomenclature, provide its molecular formula.
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C18H20BrClN2O2
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