You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[2-(1-ethyl-3,5-dimethylpyrazol-4-yl)ethyl]-1-propanoyl-2,3-dihydroindole-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H28N4O2
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