### BUGGY CODE ###

"""
    Satwik_Tiwari ;) .
    21st AUGUST , 2020  - FRIDAY
"""

#===============================================================================================
#importing some useful libraries.
from __future__ import division, print_function

from fractions import Fraction
import sys
import os
from io import BytesIO, IOBase

from itertools import *
import bisect
from heapq import *
from math import *
from copy import *
from collections import deque
from collections import Counter as counter  # Counter(list)  return a dict with {key: count}
from itertools import combinations as comb # if a = [1,2,3] then print(list(comb(a,2))) -----> [(1, 2), (1, 3), (2, 3)]
from itertools import permutations as permutate
from bisect import bisect_left as bl
#If the element is already present in the list,
# the left most position where element has to be inserted is returned.
from bisect import bisect_right as br
from bisect import bisect
#If the element is already present in the list,
# the right most position where element has to be inserted is returned

#==============================================================================================
#fast I/O region
BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


def print(*args, **kwargs):
    """Prints the values to a stream, or to sys.stdout by default."""
    sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
    at_start = True
    for x in args:
        if not at_start:
            file.write(sep)
        file.write(str(x))
        at_start = False
    file.write(kwargs.pop("end", "\n"))
    if kwargs.pop("flush", False):
        file.flush()


if sys.version_info[0] < 3:
    sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
else:
    sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)

# inp = lambda: sys.stdin.readline().rstrip("\r\n")

#===============================================================================================
### START ITERATE RECURSION ###
from types import GeneratorType
def iterative(f, stack=[]):
  def wrapped_func(*args, **kwargs):
    if stack: return f(*args, **kwargs)
    to = f(*args, **kwargs)
    while True:
      if type(to) is GeneratorType:
        stack.append(to)
        to = next(to)
        continue
      stack.pop()
      if not stack: break
      to = stack[-1].send(to)
    return to
  return wrapped_func
#### END ITERATE RECURSION ####

#===============================================================================================
#some shortcuts

mod = 1000000007
def inp(): return sys.stdin.readline().rstrip("\r\n") #for fast input
def out(var): sys.stdout.write(str(var))  #for fast output, always take string
def lis(): return list(map(int, inp().split()))
def stringlis(): return list(map(str, inp().split()))
def sep(): return map(int, inp().split())
def strsep(): return map(str, inp().split())
# def graph(vertex): return [[] for i in range(0,vertex+1)]
def zerolist(n): return [0]*n
def nextline(): out("\n")  #as stdout.write always print sring.
def testcase(t):
    for p in range(t):
        solve()
def printlist(a) :
    for p in range(0,len(a)):
        out(str(a[p]) + ' ')
def google(p):
    print('Case #'+str(p)+': ',end='')
def lcm(a,b): return (a*b)//gcd(a,b)
def power(x, y, p) :
    res = 1     # Initialize result
    x = x % p  # Update x if it is more , than or equal to p
    if (x == 0) :
        return 0
    while (y > 0) :
        if ((y & 1) == 1) : # If y is odd, multiply, x with result
            res = (res * x) % p

        y = y >> 1      # y = y/2
        x = (x * x) % p
    return res
def ncr(n,r): return factorial(n)//(factorial(r)*factorial(max(n-r,1)))
def isPrime(n) :
    if (n <= 1) : return False
    if (n <= 3) : return True
    if (n % 2 == 0 or n % 3 == 0) : return False
    i = 5
    while(i * i <= n) :
        if (n % i == 0 or n % (i + 2) == 0) :
            return False
        i = i + 6
    return True

#===============================================================================================
# code here ;))
def djkistra(g,st,dist): #g contains b,dist(a to b) and dist is initiaalised by 10**9 initiallly
    pq = []
    dist[st] = 0
    pq.append([0,st])
    while(len(pq) != 0):
        curr = heappop(pq)[1]
        for i in range(0,len(g[curr])):
            b = g[curr][i][0]
            w = g[curr][i][1]
            if(dist[b] > dist[curr] + w):
                dist[b] = dist[curr]+w
                pq.append([dist[b],b])

def solve():
    n,m = sep()
    x,y = sep()
    xnot ,ynot = sep()
    x-=1
    y-=1
    xnot-=1
    ynot-=1

    grid = []
    for i in range(n):
        temp = list(inp())
        grid.append(temp)

    g = [[] for i in range(n*m)]

    for i in range(n):
        for j in range(m):
            if(grid[i][j] == '#'):
                continue
            for ii in range(i-2,i+3):
                for jj in range(j-2,j+3):
                    if(ii==i and jj==j):
                        continue
                    if(0<=ii<n and 0<=jj<m and grid[ii][jj] == '.'):
                        if(abs(ii-i)+abs(jj-j) == 1):
                            g[i*m+j].append([ii*m+jj,0])
                        else:
                            g[i*m+j].append([ii*m+jj,1])
                        # print(i*m+j,ii*m+jj)
    # for i in range(n*m):
    #     print(g[i])

    dist = [10**6]*(n*m)
    # print(x*m+y,xnot*m+ynot)
    djkistra(g,x*m+y,dist)
    # print(dist[xnot*m+ynot])
    # print(dist)
    if(dist[xnot*m+ynot] == 10**6):
        print(-1)
    else:
        print(dist[xnot*m+ynot])









testcase(1)
# testcase(int(inp()))















### FIXED CODE ###

INF = 10**9
import sys
from heapq import *
input = sys.stdin.readline

class Dijkstra:
    def __init__(self, adj):
        self.adj = adj
        self.dist = [INF] * len(adj)
        self.q = []

    def calc(self, start):
        self.dist[start] = 0
        heappush(self.q, (0, start))
        while len(self.q) != 0:
            prov_cost, src = heappop(self.q)
            if self.dist[src] < prov_cost:
                continue
            for dest, cost in self.adj[src]:
                if self.dist[dest] > self.dist[src] + cost:
                    self.dist[dest] = self.dist[src] + cost
                    heappush(self.q, (self.dist[dest], dest))
        return self.dist

def sep(): return map(int,input().split())
def solve():
    h,w = sep()
    x,y = sep()
    xnot ,ynot = sep()
    x-=1
    y-=1
    xnot-=1
    ynot-=1

    field = []
    for i in range(h):
        temp = input().rstrip()
        field.append(temp)

    edge = [[] for i in range(h*w)]
    for i in range(h):
        for j in range(w):
            if field[i][j] == "#":
                continue
            frm = i * w + j
            for dx in range(-2, 3):
                nx = i + dx
                if nx < 0 or nx > h - 1:
                    continue
                for dy in range(-2, 3):
                    if dx == 0 and dy == 0:
                        continue
                    ny = j + dy
                    if ny < 0 or ny > w - 1:
                        continue
                    if field[nx][ny] == "#":
                        continue
                    dist = abs(dx) + abs(dy)
                    if dist == 1:
                        edge[frm].append((nx*w + ny, 0))
                    else:
                        edge[frm].append((nx*w + ny, 1))


    # for i in range(n):
    #     for j in range(m):
    #         if(grid[i][j] == '#'):
    #             continue
    #         for ii in range(i-2,i+3):
    #             for jj in range(j-2,j+3):
    #                 if(ii==i and jj==j):
    #                     continue
    #                 if(0<=ii<n and 0<=jj<m and grid[ii][jj] == '.'):
    #                     if(abs(ii-i)+abs(jj-j) == 1):
    #                         g[i*m+j].append([ii*m+jj,0])
    #                     else:
    #                         g[i*m+j].append([ii*m+jj,1])
                        # print(i*m+j,ii*m+jj)
    # for i in range(n*m):
    #     print(g[i])

    # dist = [10**9]*(n*m)
    # print(x*m+y,xnot*m+ynot)
    d = Dijkstra(edge)
    dist = d.calc(x*w+y)
    # print(dist[xnot*m+ynot])
    # print(dist)
    if(dist[xnot*w+ynot] == 10**9):
        print(-1)
    else:
        print(dist[xnot*w+ynot])

solve()