You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(2S)-1-[(2-chloropyridin-3-yl)amino]-1-oxopropan-2-yl] (3S)-1-(2-ethylphenyl)-5-oxopyrrolidine-3-carboxylate by IUPAC nomenclature, provide its molecular formula.
user
C21H22ClN3O4
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