Buggy python submission (verdict: Time Limit Exceeded):
import sys, math
from collections import defaultdict, deque, Counter
from bisect import bisect_left, bisect_right
from itertools import combinations, permutations, product
from heapq import heappush, heappop
from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
narr = lambda d, f: narr(d[:-1], lambda: [f() for _ in range(d[-1])]) if d else f() # narr((2,3), int)
mod = 1000000007
sys.setrecursionlimit(1000000)

H, W = rl()
C = rl()
D = rl()
M = []
for i in range(H):
	s = rs()
	M.append(s)

start = tuple([C[0]-1, C[1]-1])
end = tuple([D[0]-1, D[1]-1])

queue = deque()
queue.append((start, 0))
visited = narr((H, W), lambda: float('inf'))
visited[start[0]][start[1]] = 0

ds = [(1,0),(-1,0),(0,1),(0,-1)]
while queue:
	n, d = queue.popleft()
	if n == end:
		print(d)
		exit()
	i, j = n
	if visited[i][j] != d:
		continue
	nd = d
	for di, dj in ds:
		ni, nj = i+di, j+dj
		if not (0 <= ni < H and 0 <= nj < W): continue
		if M[ni][nj] == '#': continue
		if nd < visited[ni][nj]:
			queue.appendleft(((ni,nj), nd))
			visited[ni][nj] = nd
	nd = d+1
	for di in range(-2, 3):
		for dj in range(-2, 3):
			if (di, dj) == (0,0): continue
			ni, nj = i+di, j+dj
			if not (0 <= ni < H and 0 <= nj < W): continue
			if M[ni][nj] == '#': continue
			if nd < visited[ni][nj]:
				queue.append(((ni,nj), nd))
				visited[ni][nj] = nd
print(-1)


Fixed submission:
import sys, math
from collections import defaultdict, deque, Counter
#from bisect import bisect_left, bisect_right
#from itertools import combinations, permutations, product
from heapq import heappush, heappop
#from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

dist = defaultdict(lambda: float('inf'))
def dijkstra(start, end):
	dist[start] = 0
	heap = []
	heappush(heap, (0, start))
	while heap:
		d, n = heappop(heap)
		if n == end:
			return d
		if dist[n] != d:
			continue
		edges = get_edges(n)
		for nn, ed in edges:
			nd = d + ed
			if dist[nn] > nd:
				dist[nn] = nd
				heappush(heap, (nd, nn))
	return -1

def get_edges(n):
	i, j = n
	edges = []
	if M[i][j] == '#': return edges
	for di in range(-2, +3):
		for dj in range(-2, +3):
			ni, nj = i+di, j+dj
			if di == 0 and dj == 0: continue
			if not(0 <= ni < H and 0 <= nj < W): continue
			if M[ni][nj] == '#': continue
			if (di, dj) in [(1,0),(-1,0),(0,1),(0,-1)]:
				edges.append(((ni, nj), 0))
			else:
				edges.append(((ni, nj), 1))
	return edges

H, W = rl()
C = rl()
D = rl()
M = []
for i in range(H):
	s = rs()
	M.append(s)

start = tuple([C[0]-1, C[1]-1])
end = tuple([D[0]-1, D[1]-1])
d = dijkstra(start, end)
print(d)

Buggy python submission (verdict: Time Limit Exceeded):
import sys, math
from collections import defaultdict, deque, Counter
from bisect import bisect_left, bisect_right
from itertools import combinations, permutations, product
#from heapq import heappush, heappop
from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

import heapq
def dijkstra(start, end):
	dist = defaultdict(lambda: float('inf'))
	dist[start] = 0
	heap = []
	heapq.heappush(heap, (0, start))
	while heap:
		d, n = heapq.heappop(heap)
		if n == end:
			return d
		if dist[n] != d:
			continue
		edges = get_edges(n)
		for nn, ed in edges:
			nd = d + ed
			if dist[nn] > nd:
				dist[nn] = nd
				heapq.heappush(heap, (nd, nn))
	return -1

def get_edges(n):
	i, j = n
	edges = []
	if M[i][j] == '#': return edges
	for di, dj in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
		ni, nj = i+di, j+dj
		if not (0 <= ni < H and 0 <= nj < W): continue
		if M[ni][nj] == '#': continue
		edges.append(((ni, nj), 0))
	for di in range(-2, +3):
		for dj in range(-2, +3):
			ni, nj = i+di, j+dj
			if di == 0 and dj == 0: continue
			if (di, dj) in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
				continue
			if not(0 <= ni < H and 0 <= nj < W): continue
			if M[ni][nj] == '#': continue
			edges.append(((ni, nj), 1))
	return edges

H, W = rl()
C = rl()
D = rl()
M = []
for i in range(H):
	s = rs()
	M.append(s)

start = tuple([C[0]-1, C[1]-1])
end = tuple([D[0]-1, D[1]-1])
d = dijkstra(start, end)
print(d)


Fixed submission:
import sys, math
from collections import defaultdict, deque, Counter
#from bisect import bisect_left, bisect_right
#from itertools import combinations, permutations, product
from heapq import heappush, heappop
#from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

dist = defaultdict(lambda: float('inf'))
def dijkstra(start, end):
	dist[start] = 0
	heap = []
	heappush(heap, (0, start))
	while heap:
		d, n = heappop(heap)
		if n == end:
			return d
		if dist[n] != d:
			continue
		edges = get_edges(n)
		for nn, ed in edges:
			nd = d + ed
			if dist[nn] > nd:
				dist[nn] = nd
				heappush(heap, (nd, nn))
	return -1

def get_edges(n):
	i, j = n
	edges = []
	if M[i][j] == '#': return edges
	for di in range(-2, +3):
		for dj in range(-2, +3):
			ni, nj = i+di, j+dj
			if di == 0 and dj == 0: continue
			if not(0 <= ni < H and 0 <= nj < W): continue
			if M[ni][nj] == '#': continue
			if (di, dj) in [(1,0),(-1,0),(0,1),(0,-1)]:
				edges.append(((ni, nj), 0))
			else:
				edges.append(((ni, nj), 1))
	return edges

H, W = rl()
C = rl()
D = rl()
M = []
for i in range(H):
	s = rs()
	M.append(s)

start = tuple([C[0]-1, C[1]-1])
end = tuple([D[0]-1, D[1]-1])
d = dijkstra(start, end)
print(d)

Buggy python submission (verdict: Time Limit Exceeded):
import sys, math
from collections import defaultdict, deque, Counter
from bisect import bisect_left, bisect_right
from itertools import combinations, permutations, product
#from heapq import heappush, heappop
from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

import heapq
def dijkstra(edges, start, end):
	#dist = [float('inf')]*N
	dist = defaultdict(lambda: float('inf'))
	dist[start] = 0
	heap = []
	heapq.heappush(heap, (0, start))
	while heap:
		d, n = heapq.heappop(heap)
		if n == end:
			return d
		if dist[n] != d:
			continue
		for nn, ed in edges[n]:
			nd = d + ed
			if dist[nn] > nd:
				dist[nn] = nd
				heapq.heappush(heap, (nd, nn))
	return -1

H, W = rl()
C = rl()
D = rl()
M = []
for i in range(H):
	s = rs()
	M.append(s)

edges = defaultdict(list)
for i in range(H):
	for j in range(W):
		if M[i][j] == '#': continue
		n = (i,j)
		edges[n] = []
		for di, dj in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
			ni, nj = i+di, j+dj
			if not (0 <= ni < H and 0 <= nj < W): continue
			if M[ni][nj] == '#': continue
			edges[n].append(((ni, nj), 0))
		for di in range(-2, +3):
			for dj in range(-2, +3):
				ni, nj = i+di, j+dj
				if di == 0 and dj == 0: continue
				if (di, dj) in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
					continue
				if not(0 <= ni < H and 0 <= nj < W): continue
				if M[ni][nj] == '#': continue
				edges[n].append(((ni, nj), 1))

start = tuple([C[0]-1, C[1]-1])
end = tuple([D[0]-1, D[1]-1])
d = dijkstra(edges, start, end)
print(d)


Fixed submission:
import sys, math
from collections import defaultdict, deque, Counter
#from bisect import bisect_left, bisect_right
#from itertools import combinations, permutations, product
from heapq import heappush, heappop
#from functools import lru_cache
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

dist = defaultdict(lambda: float('inf'))
def dijkstra(start, end):
	dist[start] = 0
	heap = []
	heappush(heap, (0, start))
	while heap:
		d, n = heappop(heap)
		if n == end:
			return d
		if dist[n] != d:
			continue
		edges = get_edges(n)
		for nn, ed in edges:
			nd = d + ed
			if dist[nn] > nd:
				dist[nn] = nd
				heappush(heap, (nd, nn))
	return -1

def get_edges(n):
	i, j = n
	edges = []
	if M[i][j] == '#': return edges
	for di in range(-2, +3):
		for dj in range(-2, +3):
			ni, nj = i+di, j+dj
			if di == 0 and dj == 0: continue
			if not(0 <= ni < H and 0 <= nj < W): continue
			if M[ni][nj] == '#': continue
			if (di, dj) in [(1,0),(-1,0),(0,1),(0,-1)]:
				edges.append(((ni, nj), 0))
			else:
				edges.append(((ni, nj), 1))
	return edges

H, W = rl()
C = rl()
D = rl()
M = []
for i in range(H):
	s = rs()
	M.append(s)

start = tuple([C[0]-1, C[1]-1])
end = tuple([D[0]-1, D[1]-1])
d = dijkstra(start, end)
print(d)