import queue
import math

W,H = [int(x) for x in input().split(" ")]

def Find(i,j,p,l):
    que = queue.Queue()
    tmp = []
    que.put([i,j])
    tmp.append([i,j])

    tmplist = list(l[i])
    tmplist[j] = '#'
    l[i] = "".join(tmplist)
    
    dx = [-1,0,0,1]
    dy = [0,-1,1,0]
    while not que.empty():
        t = que.get()
        for i in range(len(dx)):
            x = dx[i]
            y = dy[i]
            if t[0] + x < 0 or t[0] + x >= H or t[1] + y < 0 or t[1] + y >= W:
                continue
            
            if l[t[0]+x][t[1]+y] == '.':
                que.put([t[0]+x,t[1]+y])
                tmp.append([t[0]+x,t[1]+y])
                tmplist = list(l[t[0]+x])
                tmplist[t[1]+y] = '#'
                l[t[0]+x] = "".join(tmplist)
    p.put(tmp)
    return [p,l]

def Calc(p):
    p1 = p.get()
    p2 = p.get()
    
    m = 2000000000
    for x in p1:
        for y in p2:
            m = min(m,math.fabs(x[0]-y[0])+math.fabs(x[1]-y[1])-1)
    return int(m)
                

l = []
for i in range(H):
    l.append(input())

p = queue.Queue()
for i in range(H):
    for j in range(W):
        if l[i][j] == '.':
            p,l = Find(i,j,p,l)

res = Calc(p)
print(res)