You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 1-[[4-(difluoromethoxy)phenyl]methyl]-1,2-dimethyl-3-[(3-nitrophenyl)methyl]guanidine;hydroiodide by IUPAC nomenclature, provide its molecular formula.
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C18H21F2IN4O3
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