You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-hydroxy-8-[(2E,4Z)-1-(4-iodoimidazol-1-yl)-2-methylhexa-2,4-dienyl]-6-methyl-7,8-dihydropyrazino[1,2-b]pyridazine-3,5-dione is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20IN5O3
assistant