You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by (4R,5S)-1-(5-chloro-2-hydroxyphenyl)-5-(1-propan-2-ylpyrrol-2-yl)-4-pyridin-2-ylimidazolidine-2-thione ?
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C21H21ClN4OS
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