You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (2R)-4-[(3-ethylphenyl)carbamothioyl]-N-propyl-2,3-dihydro-1,4-benzoxazine-2-carboxamide into molecular formula.
user
C21H25N3O2S
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