You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (2S)-N-[2-(1H-indol-3-yl)ethyl]-2-(3-methyl-4-oxopyridazino[4,5-b]indol-5-yl)butanamide into its molecular formula.
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C25H25N5O2
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