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".
You are also given a referring expression that describes one of the given grids.
Your task is to select the grid that matches the given referring expression.
Generate only the number (in text) of the grid that matches the given expression by selecting first, second, or third.

First:

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

Second:

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

Third:

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

Expression: The target grid has a diagonal pattern of filled cells, with two filled cells on the top and bottom rows, and a filled cell in the center row. The filled cells in the center row are arranged in a vertical line.
Question: Which grid does the expression refer to?
Start with the tag "Answer: ", followed by your selection. Omit any other text.

Answer: second
assistant
Answer: second
assistant