You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3R)-10-acetamido-2-butyl-N-cyclohexyl-8-methoxy-3-methyl-1-oxo-4H-pyrazino[1,2-a]indole-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C26H36N4O4
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