Doraemon in the Maze

Doraemon is trapped in a rectangular maze represented as an $n \times m$ grid. Each cell in the maze is either an empty space or a wall. Doraemon can only move from one empty cell to an adjacent empty cell in the four cardinal directions: up, down, left, and right.

The starting position is at the top-left corner, i.e. cell $(1,1)$, and the goal is to reach the bottom-right corner, i.e. cell $(n,m)$.

Determine whether Doraemon can reach the destination. If he can, print YES; otherwise, print NO.

The maze cells are given as follows: a '.' (dot) represents an empty space, and a '#' (hash) represents a wall.

inputFormat

The first line contains two integers $n$ and $m$ $(1 \le n, m \le 1000)$, representing the number of rows and columns of the maze respectively.

Each of the following $n$ lines contains a string of length $m$ consisting of characters '.' and '#' that describe the maze.

outputFormat

Output a single line containing YES if Doraemon can go from cell $(1,1)$ to cell $(n,m)$ through empty cells only, or NO otherwise.

sample

3 3
...
.#.
...

YES