You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[4-[4-[[2-(azepan-1-yl)-5-oxo-6H-pyrimido[4,5-d]pyridazin-4-yl]amino]phenyl]piperazin-1-yl]-2-methylpropanoic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C26H34N8O3
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