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 ▢

Distractor grid 1:

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

Distractor grid 2:

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 the only one with two filled cells in the top row, where the last filled cell is in the first position from the right. It also uniquely features a diagonal line of filled cells starting from the top left corner to the middle of the grid.
assistant
Expression: the grid with three X's in the top row, an X in the center of the middle row, and a single X in the bottom row
assistant