You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 4-[2-[[(3,5-diamino-6-chloropyrazine-2-carbonyl)amino]methyl]-3-ethyl-5-methoxybenzimidazol-1-ium-1-yl]butanoic acid is given. What is its corresponding molecular formula?
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C20H25ClN7O4+
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