You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[1-(2-amino-3-methyl-5-pyridin-3-yl-2H-pyrazin-3-yl)ethenyl]-N'-methylthiophene-2-carboximidamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H20N6S
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