You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 5-methoxy-5'-(2-methoxypyridin-4-yl)spiro[1H-indole-3,2'-3H-1,3,4-thiadiazole]-2-one;2,2,2-trifluoroacetic acid by IUPAC nomenclature, provide its molecular formula.
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C18H15F3N4O5S
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