Maximal Rectangle in a Mall Grid

You are given a grid representing the layout of a shopping mall. Each cell in the grid is either an empty space denoted by . or a store denoted by *. Your task is to determine the area of the largest rectangle that can be formed using only store cells.

In this problem, a rectangle is defined by a contiguous block of cells aligned with the grid. The area is computed as the number of cells within the rectangle. Formally, if a rectangle has height h and width w, its area is given by $$ A = h \times w $$.

Note: The rectangle must be formed entirely by cells marked with *.

inputFormat

The input is given via standard input (stdin) and has the following format:

r
row1
row2
...
rowr

Where r is an integer representing the number of rows in the grid, and each subsequent line represents one row of the grid. Each row is a string composed of the characters . and *.

outputFormat

Output a single integer to standard output (stdout): the area of the largest rectangle that consists entirely of store cells (denoted by *).

4
.....
.***.
.***.
.....

6