W, H = map(int, input().split())
maze = [input() for i in range(H)]
dist = [[W * H for j in range(W * H)] for j in range(W * H)]

for i in range(W * H):
    dist[i][i] = 0
    for d in (-W, -1, 1, W):
        if i + d < 0 or W * H <= i + d:
            continue
        if d in (-1, 1) and (i + d) // W != i // W:
            continue
        if maze[(i + d) // W][(i + d) % W] == '#':
            dist[i][i + d] = 1
        else:
            dist[i][i + d] = 0

for k in range(W * H):
    for i in range(W * H):
        for j in range(W * H):
            dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j])

min_cost = W * H
for i in range(W+1, W*H):
    if maze[i // W][i % W] == '#':
        continue
    for j in range(i + 1, W * (H-1)):
        if maze[j // W][j % W] == '#':
            continue
        if dist[i][j] > 0:
            min_cost = min(min_cost, dist[i][j])

print(min_cost)