Buggy python submission (verdict: Runtime Error):
import numpy as np
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = [[0]*W for i in range(H)]
right = [[0]*W for i in range(H)]
up = [[0]*W for i in range(H)]
down = [[0]*W for i in range(H)]

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Fixed submission:
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = [[0]*W for i in range(H)]
right = [[0]*W for i in range(H)]
up = [[0]*W for i in range(H)]
down = [[0]*W for i in range(H)]

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = [[0]*W for i in range(H)]
right = [[0]*W for i in range(H)]
up = [[0]*W for i in range(H)]
down = [[0]*W for i in range(H)]

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Fixed submission:
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = [[0]*W for i in range(H)]
right = [[0]*W for i in range(H)]
up = [[0]*W for i in range(H)]
down = [[0]*W for i in range(H)]

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Buggy python submission (verdict: Runtime Error):
import numpy as np
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = np.zeros((H,W), dtype=int)
right = np.zeros((H,W), dtype=int)
up = np.zeros((H,W), dtype=int)
down = np.zeros((H,W), dtype=int)

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Fixed submission:
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = [[0]*W for i in range(H)]
right = [[0]*W for i in range(H)]
up = [[0]*W for i in range(H)]
down = [[0]*W for i in range(H)]

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = np.zeros((H,W), dtype=int)
right = np.zeros((H,W), dtype=int)
up = np.zeros((H,W), dtype=int)
down = np.zeros((H,W), dtype=int)

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)

Fixed submission:
from sys import stdin
H, W = [int(_) for _ in stdin.readline().rstrip().split()]
S = [stdin.readline().rstrip() for _ in range(H)]

left = [[0]*W for i in range(H)]
right = [[0]*W for i in range(H)]
up = [[0]*W for i in range(H)]
down = [[0]*W for i in range(H)]

for i in range(H):
    p = 0
    for j in range(W):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        left[i][j] = p
for i in range(H):
    p = 0
    for j in range(W)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        right[i][j] = p
for j in range(W):
    p = 0
    for i in range(H):
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        up[i][j] = p
for j in range(W):
    p = 0
    for i in range(H)[::-1]:
        if S[i][j] == '#':
            p = 0
        else:
            p += 1
        down[i][j] = p

ans = 0
for i in range(H):
    for j in range(W):
        if S[i][j] == '#':
            continue
        ans = max(ans, left[i][j] + right[i][j] + up[i][j] + down[i][j] - 3) 

print(ans)