Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict,deque
import sys,heapq,bisect,math,itertools,string,queue,datetime
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
def inpl(): return list(map(int, input().split()))
def inpl_s(): return list(input().split())

H,W = inpl()

white = 0
maze = [['#']*(W+2)]
for i in range(H):
	li = list(input())
	white += li.count('.')
	maze.append(['#'] + li + ['#'])
maze.append(['#']*(W+2))

def check(x,y,n):
	if x==W and y==H:
		print(white-n)
		sys.exit()
	elif maze[y][x] == '.':
		q.put([x-1,y,n+1])
		q.put([x+1,y,n+1])
		q.put([x,y-1,n+1])
		q.put([x,y+1,n+1])
	else:
		return

q = queue.Queue()
q.put([1,1,1])
while not q.empty():
	x,y,n = q.get()
	check(x,y,n)

print(-1)


Fixed submission:
import sys
import queue

H,W = map(int,input().split())


white = 0
	
maze = []

for y in range(H):
	li = list(input())
	white += li.count('.')
	maze.append(li)

if maze[0][0] == '#' or maze[H-1][W-1] == '#':
	print (-1)
	sys.exit()

	
maze[H-1][W-1] =	'g'
	
q = queue.Queue()
q.put([0,0,0])

def check(x,y,n):
	if 0 <= x < W and 0 <= y < H:
		if maze[y][x] == 'g':
			print (white - n - 1)
			sys.exit()
		elif maze[y][x] == '.':
			maze[y][x] = n
			q.put([x-1,y,n+1])
			q.put([x+1,y,n+1])
			q.put([x,y-1,n+1])
			q.put([x,y+1,n+1])
		else:
			return
	else:
		return


while not q.empty():
	x,y,n = q.get()
	check(x,y,n)
	
print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict,deque
import sys,heapq,bisect,math,itertools,string,queue,datetime
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
def inpl(): return list(map(int, input().split()))
def inpl_s(): return list(input().split())

H,W = inpl()

white = 0
MAP = [['#']*(W+2)]
for i in range(H):
	li = list(input())
	white += li.count('.')
	MAP.append(['#'] + li + ['#'])
MAP.append(['#']*(W+2))

memo = [[INF for x in range(W+2)] for y in range(H+2)]

def check(x,y,n):
	if MAP[y][x] == '#':
		return
	elif x==W and y==H:
		print(white-n)
		sys.exit()
	else:
		memo[y][x] = n
		q.put([x-1,y,n+1])
		q.put([x+1,y,n+1])
		q.put([x,y-1,n+1])
		q.put([x,y+1,n+1])
		return



q = queue.Queue()
q.put([1,1,1])
while not q.empty():
	x,y,n = q.get()
	check(x,y,n)

print(-1)


Fixed submission:
import sys
import queue

H,W = map(int,input().split())


white = 0
	
maze = []

for y in range(H):
	li = list(input())
	white += li.count('.')
	maze.append(li)

if maze[0][0] == '#' or maze[H-1][W-1] == '#':
	print (-1)
	sys.exit()

	
maze[H-1][W-1] =	'g'
	
q = queue.Queue()
q.put([0,0,0])

def check(x,y,n):
	if 0 <= x < W and 0 <= y < H:
		if maze[y][x] == 'g':
			print (white - n - 1)
			sys.exit()
		elif maze[y][x] == '.':
			maze[y][x] = n
			q.put([x-1,y,n+1])
			q.put([x+1,y,n+1])
			q.put([x,y-1,n+1])
			q.put([x,y+1,n+1])
		else:
			return
	else:
		return


while not q.empty():
	x,y,n = q.get()
	check(x,y,n)
	
print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict,deque
import sys,heapq,bisect,math,itertools,string,queue,datetime
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
def inpl(): return list(map(int, input().split()))
def inpl_s(): return list(input().split())

H,W = inpl()

white = 0
MAP = [['#']*(W+2)]
for i in range(H):
	li = list(input())
	white += li.count('.')
	MAP.append(['#'] + li + ['#'])
MAP.append(['#']*(W+2))

memo = [[INF for x in range(W+2)] for y in range(H+2)]
q = queue.Queue()
q.put([1,1,1])

def check(x,y,n):
	if memo[y][x] < n or MAP[y][x] == '#':
		return
	elif x==W and y==H:
		print(white-n)
		sys.exit()
	else:
		memo[y][x] = n
		q.put([x-1,y,n+1])
		q.put([x+1,y,n+1])
		q.put([x,y-1,n+1])
		q.put([x,y+1,n+1])


while not q.empty():
	x,y,n = q.get()
	check(x,y,n)

print(-1)


Fixed submission:
import sys
import queue

H,W = map(int,input().split())


white = 0
	
maze = []

for y in range(H):
	li = list(input())
	white += li.count('.')
	maze.append(li)

if maze[0][0] == '#' or maze[H-1][W-1] == '#':
	print (-1)
	sys.exit()

	
maze[H-1][W-1] =	'g'
	
q = queue.Queue()
q.put([0,0,0])

def check(x,y,n):
	if 0 <= x < W and 0 <= y < H:
		if maze[y][x] == 'g':
			print (white - n - 1)
			sys.exit()
		elif maze[y][x] == '.':
			maze[y][x] = n
			q.put([x-1,y,n+1])
			q.put([x+1,y,n+1])
			q.put([x,y-1,n+1])
			q.put([x,y+1,n+1])
		else:
			return
	else:
		return


while not q.empty():
	x,y,n = q.get()
	check(x,y,n)
	
print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict,deque
import sys,heapq,bisect,math,itertools,string,queue,datetime
sys.setrecursionlimit(10**8)
INF = float('inf')
mod = 10**9+7
eps = 10**-7
def inpl(): return list(map(int, input().split()))
def inpl_s(): return list(input().split())

H,W = inpl()

MAP = [['#']*(W+2)]
for i in range(H):
	MAP.append(['#'] + list(input()) + ['#'])
MAP.append(['#']*(W+2))

memo = [[INF for x in range(W+2)] for y in range(H+2)]
q = queue.Queue()
q.put([1,1,1])

def check(x,y,n):
	if memo[y][x] < n or MAP[y][x] == '#':
		return
	else:
		memo[y][x] = n
		q.put([x-1,y,n+1])
		q.put([x+1,y,n+1])
		q.put([x,y-1,n+1])
		q.put([x,y+1,n+1])


while not q.empty():
	x,y,n = q.get()
	check(x,y,n)

if memo[H][W] == INF:
	print(-1)
else:
	black = 0
	for y in range(1,H+1):
		for x in range(1,W+1):
			if MAP[y][x] == '#':
				black += 1
	print(H*W-black-memo[H][W])


Fixed submission:
import sys
import queue

H,W = map(int,input().split())


white = 0
	
maze = []

for y in range(H):
	li = list(input())
	white += li.count('.')
	maze.append(li)

if maze[0][0] == '#' or maze[H-1][W-1] == '#':
	print (-1)
	sys.exit()

	
maze[H-1][W-1] =	'g'
	
q = queue.Queue()
q.put([0,0,0])

def check(x,y,n):
	if 0 <= x < W and 0 <= y < H:
		if maze[y][x] == 'g':
			print (white - n - 1)
			sys.exit()
		elif maze[y][x] == '.':
			maze[y][x] = n
			q.put([x-1,y,n+1])
			q.put([x+1,y,n+1])
			q.put([x,y-1,n+1])
			q.put([x,y+1,n+1])
		else:
			return
	else:
		return


while not q.empty():
	x,y,n = q.get()
	check(x,y,n)
	
print(-1)