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 (E)-2-cyano-3-[2-(2,6-dimethylmorpholin-4-yl)-9-methyl-4-oxopyrido[1,2-a]pyrimidin-3-yl]prop-2-enamide ?
user
C19H21N5O3
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