题目描述
Constraints
- H is an integer between 2 and 50 (inclusive).
- W is an integer between 2 and 50 (inclusive).
- s_{i, j} is
.or#$(1 \leq i \leq H, 1 \leq j \leq W)$. - s_{1, 1} and s_{H, W} are
..
Input
Input is given from Standard Input in the following format:
<dl> <dt>H W</dt> <dt>s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}</dt> <dt>s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}</dt> <dd>:s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}</dd> </dl>
Output
Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.
Examples
Input
3 3
..#
..
...
Output
2
Input
3 3
..#
..
...
Output
2
Input
10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................
Output
209
输入格式
见题面
输出格式
见题面
样例输入
10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................
样例输出
209