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

start = (Ch, Cw)

S = ['#'*(W+4)]
S.append('#'*(W+4))
for k in range(H):
  S.append('##' + input() + '##')
S.append('#'*(W+4))
S.append('#'*(W+4))

counter = [[-1 for _ in range(W+4)] for _ in range(H+4)]
for k in range(2, H+2):
  for j in range(2, W+2):
    if S[k][j] == '.':
      counter[k][j] = 10**7

counter[Ch][Cw] = 0

#print(counter)
#print(S)

now = [start]
now_2 = [start]
while len(now_2) > 0:
  new = []
  for item in now_2:
    x = item[0]
    y = item[1]
    if counter[x+1][y] == 10**7:
      counter[x+1][y] = 0
      new.append((x+1, y))
    if counter[x][y+1] == 10**7:
      counter[x][y+1] = 0
      new.append((x, y+1))
    if counter[x-1][y] == 10**7:
      counter[x-1][y] = 0
      new.append((x-1, y))
    if counter[x][y-1] == 10**7:
      counter[x][y-1] = 0
      new.append((x, y-1))
  now += new
  now_2 = new
#print(now)
#print(counter)
if counter[Dh][Dw] == 0:
  print(0)
  exit()
ans = 0
while counter[Dh][Dw] == 10**7:
  if len(now) == 0:
    print(-1)
    exit() 
  nextlist = []
  ans += 1
  for item in now:
    x = item[0]
    y = item[1]
    if counter[x+2][y+2] > ans:
      counter[x+2][y+2] = ans
      nextlist.append((x+2, y+2))
    if counter[x+2][y+1] > ans:
      counter[x+2][y+1] = ans
      nextlist.append((x+2, y+1))
    if counter[x+2][y] > ans:
      counter[x+2][y] = ans
      nextlist.append((x+2, y))
    if counter[x+2][y-1] > ans:
      counter[x+2][y-1] = ans
      nextlist.append((x+2, y-1))
    if counter[x+2][y-2] > ans:
      counter[x+2][y-2] = ans
      nextlist.append((x+2, y-2))
    if counter[x+1][y+2] > ans:
      counter[x+1][y+2] = ans
      nextlist.append((x+1, y+2))
    if counter[x+1][y-2] > ans:
      counter[x+1][y-2] = ans
      nextlist.append((x+1, y-2))
    if counter[x][y+2] > ans:
      counter[x][y+2] = ans
      nextlist.append((x, y+2))
    if counter[x][y-2] > ans:
      counter[x][y-2] = ans
      nextlist.append((x, y-2))
    if counter[x-2][y+2] > ans:
      counter[x-2][y+2] = ans
      nextlist.append((x-2, y+2))
    if counter[x-2][y+1] > ans:
      counter[x-2][y+1] = ans
      nextlist.append((x-2, y+1))
    if counter[x-2][y] > ans:
      counter[x-2][y] = ans
      nextlist.append((x-2, y))
    if counter[x-2][y-1] > ans:
      counter[x-2][y-1] = ans
      nextlist.append((x-2, y-1))
    if counter[x-2][y-2] > ans:
      counter[x-2][y-2] = ans
      nextlist.append((x-2, y-2))
    if counter[x-1][y+2] > ans:
      counter[x-1][y+2] = ans
      nextlist.append((x-1, y+2))
    if counter[x-1][y-2] > ans:
      counter[x-1][y-2] = ans
      nextlist.append((x-1, y-2))
    if counter[x-1][y-1] > ans:
      counter[x-1][y-1] = ans
      nextlist.append((x-1, y-1))
    if counter[x-1][y+1] > ans:
      counter[x-1][y+1] = ans
      nextlist.append((x-1, y+1))
    if counter[x+1][y+1] > ans:
      counter[x+1][y+1] = ans
      nextlist.append((x+1, y+1))
    if counter[x+1][y-1] > ans:
      counter[x+1][y-1] = ans
      nextlist.append((x+1, y-1))
      
  
  now_2 = nextlist
  while len(now_2) > 0:
    new = []
    for item in now_2:
      x = item[0]
      y = item[1]
      if counter[x+1][y] == 10**7:
        counter[x+1][y] = 0
        new.append((x+1, y))
      if counter[x][y+1] == 10**7:
        counter[x][y+1] = 0
        new.append((x, y+1))
      if counter[x-1][y] == 10**7:
        counter[x-1][y] = 0
        new.append((x-1, y))
      if counter[x][y-1] == 10**7:
        counter[x][y-1] = 0
        new.append((x, y-1))
    nextlist += new
    now_2 = new
  now = nextlist
  #print(now)
  if ans > 10**7:
    print(-1)
    exit()
print(ans)      
    

Measured memory_bytes: 94768