Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    count = 0
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)

Fixed submission:
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    count = 0
    for i in m:
        jj = set(i)
        if len(jj) == 2:
            break
    else:
        break
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)

Fixed submission:
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

while q:
    v = q.popleft()
    count = 0
    for i in m:
        jj = set(i)
        if len(jj) == 2:
            break
    else:
        break
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1

######
ans = 0
for i in d:
    ans = max(ans,max(i))
print(ans)

Fixed submission:
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

h,w = [int(x) for x in input().split()]
m = [list(input()) for x in range(h)]

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

while q:
    v = q.popleft()
    count = 0
    for i in m:
        jj = set(i)
        if len(jj) == 2:
            break
    else:
        break
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1

######
ans = 0
for i in d:
    ans = max(ans,max(i))
print(ans)

Fixed submission:
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

h,w = [int(x) for x in input().split()]
m = [list(input()) for x in range(h)]

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

while q:
    v = q.popleft()
    count = 0
    for i in m:
        count += i.count("#")
    if count == h*w:
        break
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1

######
ans = 0
for i in d:
    ans = max(ans,max(i))
print(ans)


Fixed submission:
from collections import deque

h,w = [int(x) for x in input().split()]
m = []
for _ in range(h):
    m.append(list(input()))

q = deque()
d = [[-1]*w for x in range(h)]

for i in range(h):
    for j in range(w):
        if m[i][j] == "#":
            q.append([i,j])
            d[i][j] = 0

aa = 0
while q:
    v = q.popleft()
    for i in [[1,0],[-1,0],[0,1],[0,-1]]:
        ny = v[0] + i[0]
        nx = v[1] + i[1]
        if (0<=ny<h and 0<=nx<w and m[ny][nx] == "."):
            m[ny][nx] = "#"
            q.append([ny,nx])
            d[ny][nx] = d[v[0]][v[1]] + 1
            aa = max(aa,d[ny][nx])

######
print(aa)