You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[2-[[(5E,8E,11E,14E,17E)-icosa-5,8,11,14,17-pentaenoyl]amino]ethyl]-5-methyl-4-oxidopyrazin-4-ium-2-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C28H40N4O3
assistant