You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(1R)-1-[(1S,2S,4R)-2-bicyclo[2.2.1]heptanyl]ethyl]-5-methylpyrazine-2-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C15H21N3O
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