Find a path from the yellow square to the red square going through all the green squares without retracing your steps or crossing your previous path, moving only up, down, left or right at each move--never diagonally. The black squares are not to be entered or crossed.

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From Page-a-Day Amazing Mind Benders Calendar 2014, Workman Publishing, New York, by Puzzability (Mike Shenk, Amy Goldstein, Robert Leighton). Puzzle for September 10.