You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule N-[(3R,3aR,6S,6aS)-3-[[4-(3-fluorophenyl)pyrimidin-2-yl]amino]-2,3,3a,5,6,6a-hexahydrofuro[3,2-b]furan-6-yl]cyclopropanecarboxamide into molecular formula.
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C20H21FN4O3
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