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-chloro-4-fluorophenyl)-[3-(5-fluoropyridin-2-yl)-6,8-dihydro-5H-imidazo[1,2-a]pyrazin-7-yl]methanone by IUPAC nomenclature, provide its molecular formula.
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C18H13ClF2N4O
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