### BUGGY CODE ###

# coding:utf-8

import sys
import math
import time
#import numpy as np
import collections
from collections import deque
from collections import Counter
import queue
import copy
import bisect
import heapq
import itertools

def bfs(sx, sy):
  que = deque([[sy,sx]])
  D =  [(0,1), (1,0), (0,-1), (-1,0)]

  DD =  [(-2,-2), (-2,-1), (-2,0), (-2,1), (-2, 2), \
  (-1,-2), (-1,-1), (-1,1), (-1, 2), \
  (0, -2), (0, 2), \
  (1,-2), (1,-1), (1,1), (1, 2), \
  (2,-2), (2,-1), (2,0), (2,1), (2, 2) ]

  while que:
    y,x = que.popleft()
    flag = 0
    for i,j in D:
      if(x+i<0 or y+j<0 or x+i>W-1 or y+j>H-1):
        continue
      dist = G[y+j][x+i]
      if(G[y+j][x+i] != "#"):
        if(type(G[y+j][x+i]) is str):
          G[y+j][x+i] = G[y][x]
          que.append([y+j,x+i])
        elif(dist>G[y][x]):
          G[y+j][x+i] = G[y][x]
          que.append([y+j,x+i])
      else:
        flag = 1
      if(flag == 1):
          flag = 0
          for k,l in DD:
              if(x+k<0 or y+l<0 or x+k>W-1 or y+l>H-1):
                  continue
              dist = G[y+l][x+k]
              #print(G[y][x])
              if(G[y+l][x+k] != "#"):
                  if(type(G[y+l][x+k]) is str):
                      G[y+l][x+k] = G[y][x]+1
                      que.appendleft([y+l,x+k])
                  elif(dist>G[y][x]+1):
                      G[y+l][x+k] = G[y][x]+1
                      que.appendleft([y+l,x+k])

sys.setrecursionlimit(10**7)
#N, Q = map(int, input().split())
#G = [list(input()) for i in range(H)]
#INF = V * 10001
#A = [int(i) for i in input().split()]
#AB = [list(map(int, input().split())) for _ in range(K)]

H, W = map(int, input().split())
magicY, magicX = map(int, input().split())
goalY, goalX = map(int, input().split())
G = [list(input()) for i in range(H)]
G[magicY-1][magicX-1] = 0
ans = 0

#print(G[magicX-1][magicY-1])

bfs(magicX-1, magicY-1)

if(G[goalY-1][goalX-1]=="."):
    print(-1)
else:
    print(G[goalY-1][goalX-1])


### FIXED CODE ###

# coding:utf-8

import sys
import math
import time
#import numpy as np
import collections
from collections import deque
from collections import Counter
import queue
import copy
import bisect
import heapq
import itertools

def bfs(sx, sy):
  que = deque([[sy,sx]])
  D =  [(0,1), (1,0), (0,-1), (-1,0)]

  DD =  [(-2,-2), (-2,-1), (-2,0), (-2,1), (-2, 2), \
  (-1,-2), (-1,-1), (-1,1), (-1, 2), \
  (0, -2), (0, 2), \
  (1,-2), (1,-1), (1,1), (1, 2), \
  (2,-2), (2,-1), (2,0), (2,1), (2, 2) ]

  while que:
    y,x = que.popleft()
    flag = 0
    for i,j in D:
      if(x+i<0 or y+j<0 or x+i>W-1 or y+j>H-1):
        continue
      dist = G[y+j][x+i]
      if(G[y+j][x+i] != "#"):
        if(type(G[y+j][x+i]) is str):
          G[y+j][x+i] = G[y][x]
          que.appendleft([y+j,x+i])
        elif(dist>G[y][x]):
          G[y+j][x+i] = G[y][x]
          que.appendleft([y+j,x+i])
      else:
        flag = 1
      if(flag == 1):
          flag = 0
          for k,l in DD:
              if(x+k<0 or y+l<0 or x+k>W-1 or y+l>H-1):
                  continue
              dist = G[y+l][x+k]
              #print(G[y][x])
              if(G[y+l][x+k] != "#"):
                  if(type(G[y+l][x+k]) is str):
                      G[y+l][x+k] = G[y][x]+1
                      que.append([y+l,x+k])
                  elif(dist>G[y][x]+1):
                      G[y+l][x+k] = G[y][x]+1
                      que.append([y+l,x+k])

sys.setrecursionlimit(10**7)
#N, Q = map(int, input().split())
#G = [list(input()) for i in range(H)]
#INF = V * 10001
#A = [int(i) for i in input().split()]
#AB = [list(map(int, input().split())) for _ in range(K)]

H, W = map(int, input().split())
magicY, magicX = map(int, input().split())
goalY, goalX = map(int, input().split())
G = [list(input()) for i in range(H)]
G[magicY-1][magicX-1] = 0
ans = 0

#print(G[magicX-1][magicY-1])

bfs(magicX-1, magicY-1)

if(G[goalY-1][goalX-1]=="."):
    print(-1)
else:
    print(G[goalY-1][goalX-1])