You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[(4aR,8aS)-6-(3-fluorobenzoyl)-2,3,4,4a,5,7,8,8a-octahydro-1,6-naphthyridin-1-yl]but-2-yn-1-one by IUPAC nomenclature, provide its molecular formula.
user
C19H21FN2O2
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