Score : $400$ points
There is a $H \times W$-square grid with $H$ horizontal rows and $W$ vertical columns. Let $(i, j)$ denote the square at the $i$-th row from the top and $j$-th column from the left.
Each square is described by a character $C_{i, j}$, where $C_{i, j} = $ . means $(i, j)$ is an empty square, and $C_{i, j} = $ # means $(i, j)$ is a wall.
Takahashi is about to start walking in this grid. When he is on $(i, j)$, he can go to $(i, j + 1)$ or $(i + 1, j)$. However, he cannot exit the grid or enter a wall square. He will stop when there is no more square to go to.
When starting on $(1, 1)$, at most how many squares can Takahashi visit before he stops?
. or $C_{i, j} = $ #. $(1 \leq i \leq H, 1 \leq j \leq W)$.Input is given from Standard Input in the following format:
$H$ $W$
$C_{1, 1} \ldots C_{1, W}$
$\vdots$
$C_{H, 1} \ldots C_{H, W}$
Print the answer.
3 4 .#.. ..#. ..##
4
For example, by going $(1, 1) \rightarrow (2, 1) \rightarrow (2, 2) \rightarrow (3, 2)$, he can visit $4$ squares.
He cannot visit $5$ or more squares, so we should print $4$.
1 1 .
1
5 5 ..... ..... ..... ..... .....
9