You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named (3S)-3-[2-[5-(8-aminopyrido[3,4-d]pyrimidin-2-yl)-2-methylphenyl]ethynyl]-3-hydroxy-1-methylpyrrolidin-2-one is given. What is its corresponding molecular formula?
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C21H19N5O2
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