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-[2-chloro-5-[(2,2-difluoro-2-pyridin-2-ylethyl)amino]-3-[(3-fluoro-4-methylpyridin-2-yl)methyl]-6-oxopyrazin-1-yl]acetamide by IUPAC nomenclature, provide its molecular formula.
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C20H18ClF3N6O2
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