def bfs(sy: int, sx: int, num: int) -> None:
    dist[sy][sx] = num
    q = deque()
    q.append((sy, sx))
    while q:
        vy, vx = q.popleft()
        for dy, dx in ((1, 0), (-1, 0), (0, 1), (0, -1)):
            y = vy + dy
            x = vx + dx
            if not (0 <= x < w and 0 <= y < h):
                continue
            if grid[y][x] == "#":
                continue
            if dist[y][x] != -1:
                continue
            dist[y][x] = dist[vy][vx]
            q.append((y, x))

w, h = map(int, input().split())
grid = [list(input()) for _ in range(h)]
from collections import deque
dist = [[-1] * w for _ in range(h)]
cnt = 1
for i in range(h):
    for j in range(w):
        if grid[i][j] == "." and dist[i][j] == -1:
            bfs(i, j, 1000 * cnt)
            cnt += 1

a = []
b = []
for i in range(h):
    for j in range(w):
        if dist[i][j] == 1000:
            a.append((i, j))
        if dist[i][j] == 2000:
            b.append((i, j))

ans = 10 ** 18
for xi, yi in a:
    for xj, yj in b:
        ans = min(ans, abs(xi - xj) + abs(yi - yj))

print(ans - 1)