### BUGGY CODE ###

from sys import *
H, W = map(int, stdin.readline().split())
personY, personX = map(int, stdin.readline().split())
gH, gW = map(int, stdin.readline().split())

grid = [list(stdin.readline().strip()) for x in range(H)]
visited = [[10**10 for j in range(W)] for i in range(H)]
options = [(personY-1, personX-1)]

visited[personY-1][personX-1] = 0
while(options):
    y,x = options.pop()

    if y+1 < H and  grid[y+1][x] == ".":
        if visited[y+1][x] > visited[y][x]:
            options.append((y+1, x))
            visited[y+1][x] = visited[y][x]

    if  y-1 >= 0 and grid[y-1][x] == ".":
        if visited[y-1][x] > visited[y][x]:
            options.append((y-1, x))
            visited[y-1][x] = visited[y][x]

    if x+1 < W and grid[y][x+1] == ".":
        if visited[y][x+1] > visited[y][x]:
            options.append((y, x+1))
            visited[y][x+1] = visited[y][x]

    if x-1 >= 0 and grid[y][x-1] == ".":
        if visited[y][x-1] > visited[y][x]:
            options.append((y, x-1))
            visited[y][x-1] = visited[y][x]
   #-------------------------------------------
    for Y,X in [(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)]:
       if x+X >= 0 and x+X < W and y+Y >= 0 and y+Y < H and grid[y+Y][x+X] == ".":
           if visited[y+Y][x+X] > visited[y][x] +1:
               options.append((y+Y, x+X))
               visited[y+Y][x+X] = visited[y][x]+1

print(-1 if visited[gH-1][gW-1] == 10**10 else visited[gH-1][gW-1] )


### FIXED CODE ###

from sys import *
from collections import deque
H, W = map(int, stdin.readline().split())
personY, personX = map(int, stdin.readline().split())
gH, gW = map(int, stdin.readline().split())

grid = [list(stdin.readline().strip()) for x in range(H)]
visited = [ [10**10] * W for i in range(H)]
options = deque([[personY-1, personX-1]])

visited[personY-1][personX-1] = 0
while(options):
    y,x = options.popleft()
    if y+1 < H and  grid[y+1][x] == ".":
        if visited[y+1][x] > visited[y][x]:
            options.appendleft((y+1, x))
            visited[y+1][x] = visited[y][x]

    if  y-1 >= 0 and grid[y-1][x] == ".":
        if visited[y-1][x] > visited[y][x]:
            options.appendleft((y-1, x))
            visited[y-1][x] = visited[y][x]

    if x+1 < W and grid[y][x+1] == ".":
        if visited[y][x+1] > visited[y][x]:
            options.appendleft((y, x+1))
            visited[y][x+1] = visited[y][x]

    if x-1 >= 0 and grid[y][x-1] == ".":
        if visited[y][x-1] > visited[y][x]:
            options.appendleft((y, x-1))
            visited[y][x-1] = visited[y][x]
   #-------------------------------------------
    for Y,X in [(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)]:
       if x+X >= 0 and x+X < W and y+Y >= 0 and y+Y < H and grid[y+Y][x+X] == ".":
           if visited[y+Y][x+X] > visited[y][x] +1:
               options.append((y+Y, x+X))
               visited[y+Y][x+X] = visited[y][x]+1

print(-1 if visited[gH-1][gW-1] == 10**10 else visited[gH-1][gW-1] )