### BUGGY CODE ###

#!/usr/bin/env python3

import collections
import sys
input=sys.stdin.readline

import heapq

#edgeには[weight,v]を追加していく
def dijkstra(s,edge,n):
    #始点sから各頂点への最短距離
    d = [float("inf")] * n
    used = [True] * n #True:未確定
    d[s] = 0
    used[s] = False
    edgelist = []
    for e in edge[s]:
        heapq.heappush(edgelist,e)
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        #まだ使われてない頂点の中から最小の距離のものを探す
        if not used[minedge[1]]:
            continue
        v = minedge[1]
        d[v] = minedge[0]
        used[v] = False
        for e in edge[v]:
            if used[e[1]]:
                heapq.heappush(edgelist,[e[0]+d[v],e[1]])
    return d

class UnionFind():
  def __init__(self,n):
    self.n=n
    self.root=[-1]*(n+1)
    self.rank=[0]*(n+1)
  def FindRoot(self,x):
    if self.root[x]<0:
      return x
    else:
      self.root[x]=self.FindRoot(self.root[x])
      return self.root[x]
  def Unite(self,x,y):
    x=self.FindRoot(x)
    y=self.FindRoot(y)
    if x==y:
      return
    else:
      if self.rank[x]>self.rank[y]:
        self.root[x]+=self.root[y]
        self.root[y]=x
      elif self.rank[x]<=self.rank[y]:
        self.root[y]+=self.root[x]
        self.root[x]=y
        if self.rank[x]==self.rank[y]:
          self.rank[y]+=1
  def isSameGroup(self,x,y):
    return self.FindRoot(x)==self.FindRoot(y)
  def Count(self,x):
    return -self.root[self.FindRoot(x)]

h,w=map(int,input().split())
sy,sx=map(int,input().split())
gy,gx=map(int,input().split())
board=''
for _ in range(h):
    board+=input().replace('\n','')
uf=UnionFind(h*w)
for y in range(h):
    for x in range(w):
        v=y*w+x
        if board[v]=='#':
            continue
        if y-1>=0 and board[v-w]=='.':
            uf.Unite(v,v-w)
        if y+1<h and board[v+w]=='.':
            uf.Unite(v,v+w)
        if x-1>=0 and board[v-1]=='.':
            uf.Unite(v,v-1)
        if x+1<w and board[v+1]=='.':
            uf.Unite(v,v+1)
edges=[[] for _ in range(h*w+1)]
checked=set()
for y in range(h):
    for x in range(w):
        if board[y*w+x]=='#':
            continue
        for dy in [-2,-1,0,1,2]:
            if y+dy<0 or y+dy>=h:
                continue
            for dx in [-2,-1,0,1,2]:
                if x+dx<0 or x+dx>=w:
                    continue
                if board[(y+dy)*w+(x+dx)]=='#':
                    continue
                r1=uf.FindRoot(y*w+x)
                r2=uf.FindRoot((y+dy)*w+x+dx)
                if (r1,r2) in checked:
                    continue
                if r1!=r2:
                    edges[r1].append([1,r2])
                    checked.add((r1,r2))
dist=dijkstra(uf.FindRoot((sy-1)*w+(sx-1)),edges,h*w)
ans=dist[uf.FindRoot((gy-1)*w+(gx-1))]
if ans==float('inf'):
    print(-1)
else:
    print(ans)

### FIXED CODE ###

#!/usr/bin/env python3

import collections
import sys
input=sys.stdin.readline

h,w=map(int,input().split())
sy,sx=map(int,input().split())
gy,gx=map(int,input().split())
board=[['#']*(w+2)]+[list('#'+input().replace('\n','')+'#') for _ in range(h)]+[['#']*(w+2)]
scores=[[10**18]*(w+2) for _ in range(h+2)]
scores[sy][sx]=0
q=collections.deque()
q.append((sy,sx))
count=0
while len(q)!=0:
  y,x=q.popleft()
  for dx,dy in [[-1,0],[1,0],[0,-1],[0,1]]:
    if 1<=x+dx<=w and 1<=y+dy<=h and board[y+dy][x+dx]!='#' and scores[y+dy][x+dx]>scores[y][x]:
      scores[y+dy][x+dx]=scores[y][x]
      q.appendleft((y+dy,x+dx))
  for dy in range(-2,3):
    for dx in range(-2,3):
      if dx==0 and dy==0:
        continue
      if 1<=x+dx<=w and 1<=y+dy<=h and board[y+dy][x+dx]!='#' and scores[y+dy][x+dx]>scores[y][x]+1:
        scores[y+dy][x+dx]=scores[y][x]+1
        q.append((y+dy,x+dx))
if scores[gy][gx]==10**18:
    print(-1)
else:
    print(scores[gy][gx])