You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (4S)-1'-[5-[2-(trifluoromethyl)pyridin-3-yl]sulfanyl-3H-imidazo[4,5-b]pyrazin-2-yl]spiro[4,6-dihydropyrrolo[1,2-b]pyrazole-5,4'-piperidine]-4-amine into its molecular formula.
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C21H20F3N9S
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