You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-N-(4-ethylphenyl)-2-[(3-methyl-2-oxo-1,3-benzoxazol-6-yl)sulfonylamino]-4-methylsulfanylbutanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H25N3O5S2
assistant