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 ▢
X ▢ ▢ ▢ X

Second:

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

Third:

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

Expression: The target grid has a filled cell in the top-left and bottom-right corners, with a diagonal line of filled cells running from the top-left to the bottom-right. The middle column has three filled cells, and the second and fourth columns each have one filled cell.
Question: Which grid does the expression refer to?
Start with the tag "Answer: ", followed by your selection. Omit any other text.

Answer: first
assistant
Answer: first
assistant