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

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 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 target grid is a 5x5 grid with four horizontal lines and four vertical lines, where the cells in the middle row and middle column are filled with "X" and the remaining cells are empty.
assistant
Expression: Grid with two diagonal lines of empty cells
assistant