You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance methyl (1S,3R,3aR,6aR)-1-(4-hydroxyphenyl)-5-methyl-3-(2-methylsulfanylethyl)-4,6-dioxo-1,2,3a,6a-tetrahydropyrrolo[3,4-c]pyrrol-2-ium-3-carboxylate .
user
C18H23N2O5S+
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