You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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(E)-3-[3-[6-(4-methyl-1,4-diazepan-4-ium-1-yl)pyrazin-2-yl]phenyl]prop-2-enoate is the IUPAC name of a molecule. Please give its molecular formula.
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C19H22N4O2
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