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

Distractor grid 1:

▢ 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 ▢ ▢

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 two rows having two "X" marks each, followed by three rows with three "X" marks each, and the bottom row filled entirely with "X" marks.
assistant
Expression: The grid with a staircase pattern of X's, where each row has one more X than the one above it, and the bottom row is completely filled with X's.
assistant