### Hint #3 for Bernard Lemaire's puzzle: dissecting a cross to a square

Bernard Lemaire still wants you to find a 5-piece dissection of the following cross to a square. (Is he now getting a bit impatient?)

The first hint led you to learn that the square would be 7 on a side. The second hint said to overlay the square on top of the cross, so that all of the top arm of the cross and all of the right arm of the cross would be within the square.
If you look at the upper left corner of the square, you need a piece that is one unit wide to fill in on the left. In fact, the left edge of the left arm of the cross will fit nicely. Similarly, the bottom edge of the bottom arm of the cross will fill the lower right part of the square. But you need to take care: Where will the piece to fill the upper right corner of the square come from? Now cutting a thin piece off the left of the left arm suggests where to get the piece to fill the upper right corner.
Try working with this idea for a while. You are right that it's not easy. That's what makes it an interesting puzzle! When you get stuck, here's the solution.