You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named N-[(1R)-1-(6-chloro-1H-benzimidazol-2-yl)-2-methoxyethyl]-2-[4-(4-chlorophenyl)piperazin-1-yl]-5-oxo-6,7-dihydrothieno[3,2-d]pyrimidin-4-amine by IUPAC nomenclature, provide its molecular formula.
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C26H27Cl2N7O2S
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