Path Existence in a Grid

You are given a grid with N rows and M columns. Each cell in the grid is either empty (denoted by a .) or blocked (denoted by a #). The top row of the grid is considered row 0 and the bottom row is row N-1. Similarly, the left-most column is column 0 and the right-most is column M-1.

Your task is to determine whether there exists a path from the bottom-left cell (i.e., cell \( (N-1,0) \)) to the top-right cell (i.e., cell \( (0,M-1) \)). You can move one cell at a time in one of the four cardinal directions: up, down, left, or right, and you can only move through empty cells.

If the starting or ending cell is blocked, then the answer is immediately "No". Otherwise, output "Yes" if a valid path exists and "No" if it does not.

inputFormat

The input is read from standard input and contains:

• A line with two space-separated integers: N and M, representing the number of rows and columns respectively.
• N lines follow, each line contains a string of length M consisting only of the characters . and #, representing the grid. The first line corresponds to the top row of the grid.

outputFormat

Output a single line to standard output: Yes if there is a valid path from the bottom-left cell to the top-right cell, or No otherwise.

## sample

3 3
...
.#.
...

Yes

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