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 can be identified by having three X's in the top row with each X separated by an empty cell, two X's in the second row positioned at the fourth and fifth cells, and a single X in the middle of the third row. Additionally, the fourth row has an X in the first and third cells, and the fifth row has two consecutive X's starting from the second cell.
assistant
Expression: The grid with X marks in a diagonal pattern from the top left to the bottom right corner.
assistant