You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [3-[(2-fluoro-4-iodophenyl)methyl]-1-oxidopyridin-1-ium-4-yl]-[3-hydroxy-3-[(2S)-piperidin-2-yl]azetidin-1-yl]methanone by IUPAC nomenclature, provide its molecular formula.
user
C21H23FIN3O3
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