You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-amino-4-[(2S)-2-(5-chloro-4-oxo-3-phenylpyrrolo[2,1-f][1,2,4]triazin-2-yl)azetidin-1-yl]-6-ethylpyrido[4,3-d]pyrimidin-5-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C24H21ClN8O2
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