You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(2-methyl-3,4-dihydro-1H-isoquinolin-3-yl)methyl]-6-oxo-1H-pyrazine-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C16H18N4O2
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