You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 3-fluoro-9-(4-fluorophenyl)-2-(4-methylpiperazin-1-yl)-6-oxopyrido[1,2-a]pyrimidine-7-carboxylic acid into its molecular formula.
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C20H18F2N4O3
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