You are given three grids, where each of them is 5 by 5 in size.
Grids have empty cells marked with "▢" and filled cells marked with "X".
Your task is to generate a referring expression that best describes the target grid while distinguishing it from the two other distractor grids.
The first grid is the target grid, and the following two grids are the distractors.

Target grid:

X X X X X
X X X X ▢
X X X ▢ ▢
X X ▢ ▢ ▢
X ▢ ▢ ▢ ▢

Distractor grid 1:

▢ ▢ ▢ ▢ X
▢ ▢ ▢ X ▢
▢ ▢ X ▢ ▢
▢ X ▢ ▢ ▢
X ▢ ▢ ▢ ▢

Distractor grid 2:

X ▢ ▢ ▢ X
▢ X ▢ X ▢
▢ ▢ X ▢ ▢
▢ X ▢ X ▢
X ▢ ▢ ▢ X

Instruction: Describe the target grid.
Generate the referring expression starting with the tag "Expression: " for the given target grid. Omit any other text.
Expression: The grid with the top row fully filled and the filled cells gradually decreasing in each subsequent row, forming a diagonal pattern from the top left to the bottom right.
assistant
Expression: A 5x5 grid with a unique pattern of filled cells, forming a central square and several smaller squares along the edges and corners. The filled cells are located at positions (0,0), (0,4), (1,1), (1,3), (2,2), (3,0), (3,4), (4,1), and (4,3).
assistant