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 [2-[4-(2-fluorophenyl)piperazin-1-yl]-2-oxoethyl]-methyl-[(2-methylphenyl)methyl]azanium is given. What is its corresponding molecular formula?
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C21H27FN3O+
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