w, h = map(int, input().split())
c = [input() for i in range(h)]
k = set()


def cave(v, a, b):
    if a < 0 or h <= a or b < 0 or w <= b:
        return
    if (a, b) in v:
        return
    if c[a][b] == "#":
        return

    v.add((a, b))
    k.add((a, b))
    cave(v, a-1, b)
    cave(v, a+1, b)
    cave(v, a, b-1)
    cave(v, a, b+1)


def main():
    k1, k2 = set(), set()
    for i in range(h):
        for j in range(w):
            if c[i][j] == "." and (i, j) not in k:
                if len(k1) == 0:
                    cave(k1, i, j)
                else:
                    cave(k2, i, j)

    min_num = 41
    lst1, lst2 = list(k1), list(k2)
    for i in range(len(lst1)):
        for j in range(len(lst2)):
            if abs(lst1[i][0]-lst2[j][0]) + abs(lst1[i][1]-lst2[j][1]) < min_num:
                min_num = abs(lst1[i][0]-lst2[j][0]) + abs(lst1[i][1]-lst2[j][1])

    print(min_num-1)


if __name__ == '__main__':
    main()