You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 6-ethyl-5-methyl-7-(4-methylpiperazin-4-ium-1-yl)-2-thiophen-2-ylpyrazolo[1,5-a]pyrimidine by IUPAC nomenclature, provide its molecular formula.
user
C18H24N5S+
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