2021 Fermat Problem 6

A square piece of paper has a dot in its top right corner and is lying on a table. The square is folded along its diagonal, then rotated 90^\circ clockwise about its centre, and then finally unfolded, as shown.

The resulting figure is

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Fermat contests here.