You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 1-[(2-fluorophenyl)methyl]-2-methyl-3-[2-(2-oxo-3H-indol-1-yl)ethyl]guanidine is given. What is its corresponding molecular formula?
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C19H21FN4O
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