# まずUnion Findで空洞1と2を分ける
# 後空洞1と空洞2の全点対の距離の最小値が答え
# 20*20なのでかまわず全探索

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def unite(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())

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

UF = UnionFind(H*W)
for h in range(H):
    for w in range(W):
        if w+1 < W and grid[h][w] == '.' and grid[h][w] == grid[h][w+1]:
            UF.unite(h*W+w, h*W+(w+1))
        if h+1 < H and grid[h][w] == '.' and grid[h][w] == grid[h+1][w]:
            UF.unite(h*W+w, (h+1)*W+w)

ans = 10**4
for h in range(H):
    for w in range(H):
        if grid[h][w] == '.':
            for h2 in range(H):
                for w2 in range(W):
                    if grid[h2][w2] == '.':
                        if UF.find(h*W+w) != UF.find(h2*W+w2):
                            ans = min(ans, abs(h2-h)+abs(w2-w)-1)
print(ans)