### BUGGY CODE ###

# -*- coding: utf-8 -*-

from collections import deque

q = deque()

h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())

ch -= 1
cw -= 1
dh -= 1
dw -= 1

INF = 10 ** 18
# org_list = [INF for i in range(h)]
org_list = deque()
# cost_list = [[INF for j in range(w)] for i in range(h)]
cost_list = [[INF]*w for i in range(h)]

for i in range(h):
  # 文字列の入力
  s = input()
  # org_list[i] = s
  org_list.append(s)


cost_list[ch][cw] = 0

cost = 0
ph = ch
pw = cw

q.append([ph, pw])

# 上右下左
ido_h = [-1, 0, 1, 0]
ido_w = [0, 1, 0, -1]

# loopc = 3
# while 0 < loopc:
while q:

  ph, pw = q.popleft()
  cost = cost_list[ph][pw]

  for i in range(4):
    nh = ph + ido_h[i]
    nw = pw + ido_w[i]

    if nh < 0 or h -1 < nh or nw < 0 or w -1 < nw:
      continue
    val = org_list[nh][nw]
    val_cost = cost_list[nh][nw]
    if val == "#" or val_cost == cost:
      continue
    if val == "." or val_cost < val:
      cost_list[nh][nw] = cost
      q.appendleft([nh, nw])

  # ジャンプ--------------
  for i in range(-2, 3):
    if (ph + i < 0) or (h - 1 < ph + i):
      continue

    for j in range(-2, 3):
      if (pw + j < 0) or (w - 1 < pw + j) or (i==0 and j == 0) or (i==0 and j == -1) or (i==0 and j == 1) or (i==-1 and j == 0) or (i==1 and j == 0):
        continue
      if cost_list[ph + i][pw + j] <= cost:
        continue
      if org_list[ph + i][pw + j] == ".":
        cost_list[ph + i][pw + j] = cost + 1
        q.append([ph + i, pw + j])

result = cost_list[dh][dw]
if result == INF:
  result = -1

# # 最後デバッグ
# for li in org_list:
#   print(li)
# for li in cost_list:
#   print(li)


print(result)


### FIXED CODE ###

# -*- coding: utf-8 -*-

from collections import deque

q = deque()

h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())

ch -= 1
cw -= 1
dh -= 1
dw -= 1

# mylist = [[]]
ban_list = [[-1 for j in range(w)] for i in range(h)]
cost_list = [[-1 for j in range(w)] for i in range(h)]

# print(mylist)

for i in range(h):
  # 文字列の入力
  s = input()
  for j in range(len(s)):
    ban_list[i][j] = s[j]

ban_list[ch][cw] = 0
# cost_list[ch][cw] = 0

cost = 0
ph = ch
pw = cw

q.append([ph, pw])


# # 最後デバッグ
# for li in ban_list:
#   print(li)



loop = True
while loop:
  # print(len(q))
  ph, pw = q.popleft()
  cost = ban_list[ph][pw]

  # print(ph, pw)
  # print(cost)
  # 上
  if ph == 0:
    pass
  else:
    if ban_list[ph-1][pw] != "#" and ban_list[ph-1][pw] != cost:
      if ban_list[ph-1][pw] == "." or cost < ban_list[ph-1][pw]:
        ban_list[ph-1][pw] = cost
        # appendだとrandom_02.txtがWAになる
        q.appendleft([ph-1, pw])
    else:
      pass

  # 右
  if pw == w -1:
    pass
  else:
    if ban_list[ph][pw + 1] != "#" and ban_list[ph][pw + 1] != cost:
      if ban_list[ph][pw + 1] == "." or cost < ban_list[ph][pw + 1]:
        ban_list[ph][pw + 1] = cost
        q.appendleft([ph, pw+1])
    else:
      pass

  # 下
  if ph == h -1:
    pass
  else:
    if ban_list[ph+1][pw] != "#" and ban_list[ph+1][pw] != cost:
      if ban_list[ph+1][pw] == "." or cost < ban_list[ph+1][pw]:
        ban_list[ph+1][pw] = cost
        q.appendleft([ph+1, pw])
    else:
      pass

  # 左
  if pw == 0:
    pass
  else:
    if ban_list[ph][pw - 1] != "#" and ban_list[ph][pw - 1] != cost:
      if ban_list[ph][pw - 1] == "." or cost < ban_list[ph][pw - 1]:
        ban_list[ph][pw - 1] = cost
        q.appendleft([ph, pw-1])
    else:
      pass


  # ジャンプ--------------
  for i in range(-2, 3):
    if (ph + i < 0) or (h - 1 < ph + i):
      continue

    for j in range(-2, 3):
      if (pw + j < 0) or (w - 1 < pw + j) or (i==0 and j == 0) or (i==0 and j == -1) or (i==0 and j == 1) or (i==-1 and j == 0) or (i==1 and j == 0):
        continue
      if ban_list[ph + i][pw + j] == ".":
        # print(ph, pw)
        # print(i, j)
        # print(cost)
        ban_list[ph + i][pw + j] = cost + 1
        q.append([ph + i, pw + j])

  if len(q) == 0:
    loop = False


result = ban_list[dh][dw]
if result == ".":
  result = -1

# # 最後デバッグ
# for li in ban_list:
#   print(li)

print(result)