class DSU:
    def __init__(self, n):
        self._n = n
        self.parent_or_size = [-1] * n
    
    def merge(self, a, b):
        assert 0 <= a < self._n
        assert 0 <= b < self._n
        x, y = self.leader(a), self.leader(b)
        if x == y: return x
        if -self.parent_or_size[x] < -self.parent_or_size[y]: x, y = y, x
        self.parent_or_size[x] += self.parent_or_size[y]
        self.parent_or_size[y] = x
        return x

    def same(self, a, b):
        assert 0 <= a < self._n
        assert 0 <= b < self._n
        return self.leader(a) == self.leader(b)

    def leader(self, a):
        assert 0 <= a < self._n
        if self.parent_or_size[a] < 0: return a
        self.parent_or_size[a] = self.leader(self.parent_or_size[a])
        return self.parent_or_size[a]
    
    def size(self, a):
        assert 0 <= a < self._n
        return -self.parent_or_size[self.leader(a)]
    
    def groups(self):
        leader_buf = [self.leader(i) for i in range(self._n)]
        result = [[] for _ in range(self._n)]
        for i in range(self._n): result[leader_buf[i]].append(i)
        return [r for r in result if r != []]

dx = [-1, 0, 0, 1]
dy = [0, -1, 1, 0]
W, H = map(int, input().split())
C = [list(input().rstrip()) for _ in range(H)]
uf = DSU(W * H)
for i in range(H):
    for j in range(W):
        if C[i][j] == ".":
            id = i * W + j
            for k in range(4):
                ni = i + dx[k]
                nj = j + dy[k]
                if 0 > ni or ni >= H or 0 > nj or nj >= W or C[ni][nj] == "#":
                    continue
                nid = ni * W + nj
                uf.merge(id, nid)
MIN = W + H
g = []
for gr in uf.groups():
    x, y = gr[0] // W, gr[0] % W
    if C[x][y] == ".":
        g.append(gr)

for i in g[0]:
    for j in g[1]:
        x, y = i // W, i % W
        nx, ny = j // W, j % W
        #print(x, y, nx, ny)
        MIN = min(MIN, abs(x - nx) + abs(y - ny) - 1)
print(MIN)