You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 1-[2-(furan-2-yl)-2-piperidin-1-ylethyl]-3-[(3-methoxyphenyl)methyl]-2-methylguanidine;hydroiodide into molecular formula.
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C21H31IN4O2
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