The goal of the fifteen puzzle is to un-jumble its fifteen squares
by repeatedly making moves that slide squares into the empty space.
How quickly can you solve it?
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American puzzle author and mathematician Sam Loyd is often falsely
credited with creating the puzzle; indeed, Loyd claimed from 1891
until his death in 1911 that he invented it.
The puzzle was actually created around 1874 by Noyes Palmer Chapman,
a postmaster in Canastota, New York.