You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 5,6-dimethyl-2-[[4-(2-methylprop-2-enyl)piperazine-1,4-diium-1-yl]methyl]-3H-thieno[2,3-d]pyrimidin-4-one by IUPAC nomenclature, provide its molecular formula.
user
C17H26N4OS+2
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