You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-methyl-3-[1-(1-methyl-2-oxo-3H-indol-5-yl)ethyl]-1-(1-thiophen-2-ylethyl)urea is the IUPAC name of a molecule. Please give its molecular formula.
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C19H23N3O2S
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