You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (3aR,6aS)-N-[(2-chloro-4-fluorophenyl)methyl]-N-(2-fluorophenyl)-5,5-dioxo-3a,4,6,6a-tetrahydrothieno[3,4-d][1,3]thiazol-2-amine by IUPAC nomenclature, provide its molecular formula.
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C18H15ClF2N2O2S2
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