You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-[[1-(10H-pyrazino[2,3-b][1,4]benzothiazin-8-ylmethyl)-1-azoniabicyclo[2.2.2]octan-4-yl]oxy]acetic acid into molecular formula.
user
C20H23N4O3S+
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