You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (4-chlorophenyl)sulfonyl-[3-(4-methylpiperazin-4-ium-1-yl)quinoxalin-2-yl]azanide by IUPAC nomenclature, provide its molecular formula.
user
C19H20ClN5O2S
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