You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2,4-dichloro-N-[2-[[4-[2-(2-methylpropylamino)-2-oxoethyl]-1,3-thiazol-2-yl]amino]-2-oxoethyl]-N-propan-2-ylbenzamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H26Cl2N4O3S
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