def dfs(hx,hy):
	C[hy][hx] = "#"
	U[UN].add((hx,hy))
	for dx,dy in dxy:
			nx = hx + dx
			ny = hy + dy
			if 0 <= nx < W and 0 <= ny < H and C[ny][nx] == ".":
				dfs(nx,ny)
dxy = ((1,0),(0,1),(-1,0),(0,-1))
W,H = map(int,raw_input().split())
C = [list(raw_input()) for i in range(H)]
U = [set(),set()]
UN = 0
for i in range(H):
	for j in range(W):
		if C[i][j] == ".":
			dfs(j,i)
			UN += 1
print min(abs(x0-x1)+abs(y0-y1) for x0,y0 in U[0] for x1,y1 in U[1])-1