Buggy python submission (verdict: Runtime Error):
import sys
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, pi, sin, cos, radians, log2
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

ans = 0
for i in range(H):
	for j in range(W):
		ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)

print(ans)


Fixed submission:
import sys
# from collections import deque, defaultdict, Counter
# from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
# from itertools import permutations, combinations, product
# from operator import itemgetter, mul
# from copy import deepcopy
# from string import ascii_lowercase, ascii_uppercase, digits
# from numpy.fft import fft, ifft
# from fractions import gcd
# import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

# L = np.array(L)
# R = np.array(R)
# U = np.array(U)
# D = np.array(D)

ans = 0
for i in range(H):
	for j in range(W):
		ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)

print(ans)
# print((L+R+U+D).max()-3)

Buggy python submission (verdict: Runtime Error):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
# from numpy.fft import fft, ifft
from fractions import gcd
# import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]


for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

# L = np.array(L)
# R = np.array(R)
# U = np.array(U)
# D = np.array(D)

ans = 0
for i in range(H):
	for j in range(W):
		ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)

print(ans)

Fixed submission:
import sys
# from collections import deque, defaultdict, Counter
# from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
# from itertools import permutations, combinations, product
# from operator import itemgetter, mul
# from copy import deepcopy
# from string import ascii_lowercase, ascii_uppercase, digits
# from numpy.fft import fft, ifft
# from fractions import gcd
# import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

# L = np.array(L)
# R = np.array(R)
# U = np.array(U)
# D = np.array(D)

ans = 0
for i in range(H):
	for j in range(W):
		ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)

print(ans)
# print((L+R+U+D).max()-3)

Buggy python submission (verdict: Runtime Error):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from numpy.fft import fft, ifft
from fractions import gcd
import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

S = np.array(S)

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]


for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

L = np.array(L)
R = np.array(R)
U = np.array(U)
D = np.array(D)

print((L+R+U+D).max()-3)


Fixed submission:
import sys
# from collections import deque, defaultdict, Counter
# from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
# from itertools import permutations, combinations, product
# from operator import itemgetter, mul
# from copy import deepcopy
# from string import ascii_lowercase, ascii_uppercase, digits
# from numpy.fft import fft, ifft
# from fractions import gcd
# import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

# L = np.array(L)
# R = np.array(R)
# U = np.array(U)
# D = np.array(D)

ans = 0
for i in range(H):
	for j in range(W):
		ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)

print(ans)
# print((L+R+U+D).max()-3)

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
from itertools import permutations, combinations, product
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from numpy.fft import fft, ifft
from fractions import gcd
import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]


for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

L = np.array(L)
R = np.array(R)
U = np.array(U)
D = np.array(D)

print((L+R+U+D).max()-3)


Fixed submission:
import sys
# from collections import deque, defaultdict, Counter
# from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
# from itertools import permutations, combinations, product
# from operator import itemgetter, mul
# from copy import deepcopy
# from string import ascii_lowercase, ascii_uppercase, digits
# from numpy.fft import fft, ifft
# from fractions import gcd
# import numpy as np

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
MOD = 10 ** 9 + 7

H, W = MAP()
S = [input() for _ in range(H)]

L = [[0]*W for _ in range(H)]
R = [[0]*W for _ in range(H)]
D = [[0]*W for _ in range(H)]
U = [[0]*W for _ in range(H)]

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			L[i][j] = 0
		elif j == 0:
			L[i][j] = 1
		else:
			L[i][j] = L[i][j-1] + 1

for i in range(H):
	for j in range(W-1, -1, -1):
		if S[i][j] == '#':
			R[i][j] = 0
		elif j == W-1:
			R[i][j] = 1
		else:
			R[i][j] = R[i][j+1] + 1

for i in range(H):
	for j in range(W):
		if S[i][j] == '#':
			U[i][j] = 0
		elif i == 0:
			U[i][j] = 1
		else:
			U[i][j] = U[i-1][j] + 1

for i in range(H-1, -1, -1):
	for j in range(W):
		if S[i][j] == '#':
			D[i][j] = 0
		elif i == H-1:
			D[i][j] = 1
		else:
			D[i][j] = D[i+1][j] + 1

# L = np.array(L)
# R = np.array(R)
# U = np.array(U)
# D = np.array(D)

ans = 0
for i in range(H):
	for j in range(W):
		ans = max(ans, L[i][j]+R[i][j]+U[i][j]+D[i][j]-3)

print(ans)
# print((L+R+U+D).max()-3)