W,H = map(int, input().split())
C = [input() for _ in range(H)]
reached = [[0 for _ in range(W)] for __ in range(H)]
empty = []

def search(x, y):
    if x <= 0 or H <= x-1 or y <= 0 or W <= y-1 or C[x][y] == '#':
        return
    if reached[x][y]:
        return
    reached[x][y] = True
    empty.append((x, y))
    search(x+1, y)
    search(x-1, y)
    search(x, y+1)
    search(x, y-1)

for h in range(H):
    for w in range(W):
        if C[h][w] == '.':
            x1, y1 = h, w
            break
    else:
        continue
    break

search(x1, y1)
empty1 = empty[:]
empty.clear()

for h in range(H):
    for w in range(W):
        t = (h, w)
        if C[h][w] == '.' and t not in empty1:
            x2, y2 = h, w
            break
    else:
        continue
    break

search(x2, y2)

ans = []
for p in empty1:
    for q in empty:
        ans.append(abs(p[0] - q[0]) + abs(p[1] - q[1]))

print(min(ans)-1)