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 1-(2-ethylphenyl)-3-[(1R,5R)-8-(thiophen-2-ylmethyl)-8-azoniabicyclo[3.2.1]octan-3-yl]urea is given. What is its corresponding molecular formula?
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C21H28N3OS+
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