The Task

We’re given a grid with obstacles, we’re supposed to count all the reachable plots in the grid in a given number of steps (we can only move one plot at a time horizontally or vertically).

The sample input looks like this:

...........
.....###.#.
.###.##..#.
..#.#...#..
....#.#....
.##..S####.
.##..#...#.
.......##..
.##.#.####.
.##..##.##.
...........

where S is the starting position.