Buggy python submission (verdict: Time Limit Exceeded):
h, w = map(int, input().split())
s=[]
for i in range(h):
    s.append(list(input()))

l=[[0 for i in range(w)] for j in range(h)]
r=[[0 for i in range(w)] for j in range(h)]
u=[[0 for i in range(w)] for j in range(h)]
d=[[0 for i in range(w)] for j in range(h)]
for y in range(h):
    for x in range(w):
        if s[y][x] == '.':
            if x == 0:
                l[y][x]=1
            else:
                l[y][x]=l[y][x-1]+1
        
        if s[y][w-x-1] == '.':
            if x == 0:
                r[y][w-x-1]=1
            else:
                r[y][w-x-1]=r[y][w-x]+1

        if s[y][x] == '.':
            if y == 0:
                u[y][x]=1
            else:
                u[y][x]=u[y-1][x]+1
        
        if s[h-y-1][x] == '.':
            if y == 0:
                d[h-y-1][x]=1
            else:
                d[h-y-1][x]=d[h-y][x]+1

ans=0
for y in range(h):
    for x in range(w):
        val=l[y][x]+r[y][x]+u[y][x]+d[y][x]-3
        ans=max(ans, val)

print(ans)

Fixed submission:
h, w = map(int, input().split())
s=[]
for i in range(h):
    s.append(list(input()))
 
l=[[0 for i in range(w)] for j in range(h)]
r=[[0 for i in range(w)] for j in range(h)]
u=[[0 for i in range(w)] for j in range(h)]
d=[[0 for i in range(w)] for j in range(h)]
for y in range(h):
    for x in range(w):
        if s[y][x] == '.':
            if x == 0:
                l[y][x]=1
            else:
                l[y][x]=l[y][x-1]+1
        
        if s[y][w-x-1] == '.':
            if x == 0:
                r[y][w-x-1]=1
            else:
                r[y][w-x-1]=r[y][w-x]+1
 
        if s[y][x] == '.':
            if y == 0:
                u[y][x]=1
            else:
                u[y][x]=u[y-1][x]+1
        
        if s[h-y-1][x] == '.':
            if y == 0:
                d[h-y-1][x]=1
            else:
                d[h-y-1][x]=d[h-y][x]+1
 
ans=0
for y in range(h):
    for x in range(w):
        val=l[y][x]+r[y][x]+u[y][x]+d[y][x]-3
        ans=max(ans, val)
 
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
h, w = map(int, input().split())
s=[]
for i in range(h):
    s.append(list(input()))

l=[[0 for i in range(w)] for j in range(h)]
r=[[0 for i in range(w)] for j in range(h)]
u=[[0 for i in range(w)] for j in range(h)]
d=[[0 for i in range(w)] for j in range(h)]
for y in range(h):
    for x in range(w):
        if s[y][x] == '.':
            if x == 0:
                l[y][x]=1
            else:
                l[y][x]=l[y][x-1]+1
        
        if s[y][w-x-1] == '.':
            if x == 0:
                r[y][w-x-1]=1
            else:
                r[y][w-x-1]=r[y][w-x]+1

for x in range(w):
    for y in range(h):
        if s[y][x] == '.':
            if y == 0:
                u[y][x]=1
            else:
                u[y][x]=u[y-1][x]+1
        
        if s[h-y-1][x] == '.':
            if y == 0:
                d[h-y-1][x]=1
            else:
                d[h-y-1][x]=d[h-y][x]+1

ans=0
for y in range(h):
    for x in range(w):
        val=l[y][x]+r[y][x]+u[y][x]+d[y][x]-3
        ans=max(ans, val)

print(ans)

Fixed submission:
h, w = map(int, input().split())
s=[]
for i in range(h):
    s.append(list(input()))
 
l=[[0 for i in range(w)] for j in range(h)]
r=[[0 for i in range(w)] for j in range(h)]
u=[[0 for i in range(w)] for j in range(h)]
d=[[0 for i in range(w)] for j in range(h)]
for y in range(h):
    for x in range(w):
        if s[y][x] == '.':
            if x == 0:
                l[y][x]=1
            else:
                l[y][x]=l[y][x-1]+1
        
        if s[y][w-x-1] == '.':
            if x == 0:
                r[y][w-x-1]=1
            else:
                r[y][w-x-1]=r[y][w-x]+1
 
        if s[y][x] == '.':
            if y == 0:
                u[y][x]=1
            else:
                u[y][x]=u[y-1][x]+1
        
        if s[h-y-1][x] == '.':
            if y == 0:
                d[h-y-1][x]=1
            else:
                d[h-y-1][x]=d[h-y][x]+1
 
ans=0
for y in range(h):
    for x in range(w):
        val=l[y][x]+r[y][x]+u[y][x]+d[y][x]-3
        ans=max(ans, val)
 
print(ans)