from queue import Queue

def inside(x, y):
    return 0 <= x < H and 0 <= y < W

dx = [1, 0, -1, 0]
dy = [0, 1, 0, -1]

def dfs(x, y, c):
    color[x][y] = c
    for k in range(4):
        nx = x + dx[k]; ny = y + dy[k]
        if inside(nx, ny) and s[nx][ny] == '.' and color[nx][ny] == -1:
            dfs(nx, ny, c)

INF = 99
def bfs(sx, sy, gx, gy):
    que = Queue()
    que.put((sx, sy))
    d = [[INF] * W for i in range(H)]
    d[sx][sy] = 0

    while que:
        x, y = que.get()
        if (x, y) == (gx, gy):
            break
        for k in range(4):
            nx = x + dx[k]; ny = y + dy[k]
            if inside(nx, ny) and d[nx][ny] == INF:
                d[nx][ny] = d[x][y] + (s[nx][ny] == '#')
                que.put((nx, ny))

    return d[gx][gy]


W, H = map(int, input().split())
s = []
for i in range(H):
    s.append(list(input()))

color = [[-1] * W for i in range(H)]
nxtcolor = 0
for i in range(H):
    for j in range(W):
        if s[i][j] == '.' and color[i][j] == -1:
            dfs(i, j, nxtcolor)
            nxtcolor += 1

ans = INF
for i1 in range(H):
    for j1 in range(W):
        for i2 in range(H):
            for j2 in range(W):
                if color[i1][j1] == 0 and color[i2][j2] == 1:
                    ans = min(ans, bfs(i1, j1, i2, j2))
print(ans)