import sys

W, H = map(int, raw_input().split())

C = ["" for _ in xrange(H)]

matrix = [[0 for i in xrange(W)] for i in xrange(H)]


# close range
def range_check(i, mn, mx):
    return mn <= i < mx


def euclidean_distance(x, y, length):
    return abs(x) + abs(y) <= length


def dfs(C, matrix, x, y, current):
    mn = H * W

    if C[y][x] == "#" or matrix[y][x] != 0:
        return 0

    matrix[y][x] = current

    for i in xrange(-1, 2):
        for j in xrange(-1, 2):
            if i == 0 and j == 0:
                continue

            if not (range_check(x + i, 0, W) and range_check(y + j, 0, H)):
                continue
            if not euclidean_distance(i, j, 1):
                continue
            result = dfs(C, matrix, x + i, y + j, current)
            mn = min(result, mn)

    return mn


for i in xrange(H):
    C[i] = raw_input()

current = 1
for i in xrange(H):
    for j in xrange(W):
        if C[i][j] == "." and matrix[i][j] == 0:
            dfs(C, matrix, j, i, current)
            current += 1

mn = W * H
for j1 in xrange(H):
    for i1 in xrange(W):
        for j2 in xrange(H):
            for i2 in xrange(W):
                if i1 == i2 and j1 == j2:
                    continue
                if C[j1][i1] == "#" or C[j2][i2] == "#":
                    continue
                if matrix[j1][i1] == matrix[j2][i2]:
                    continue
                mn = min(mn, abs(i1 - i2) + abs(j1 - j2) - 1)

print mn