You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 1-butyl-3-[(2R)-2,4-dimethyl-3-oxo-1,4-benzoxazin-6-yl]-1-(pyridin-4-ylmethyl)urea into molecular formula.
user
C21H26N4O3
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