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 X
▢ X X X X

Distractor grid 1:

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

Distractor grid 2:

▢ X X X X
X ▢ X X X
X X ▢ X 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 a filled top-left corner, a filled bottom-right corner, and a filled cell in the center of the bottom row.
assistant
Expression: A 5x5 grid where the top row has four consecutive 'X's followed by an empty cell, and every subsequent row shifts the pattern of four 'X's and one empty cell one cell to the right, ending with the bottom row starting with an empty cell followed by four 'X's. This grid uniquely features a complete diagonal of 'X's from the top left corner to the bottom right corner, contrasting with the other grids which lack this feature.
assistant