Draw the chess board shown in the topmost
illustration or just print it out. Place a chess knight (or a simple
coin) in any cell of this board.
The object is to visit with the knight every cell
of the board exactly once, and return to the initial cell where your
trip began from.
Two bottom diagrams, a and b, show some possible moves of the chess
knight which always moves either one cell in one direction, and then
two cells in another direction, or vice versa.