Buggy python submission (verdict: Time Limit Exceeded):
from sys import stdin
readline = stdin.readline
H,W = map(int,input().split())
A = ['' for i in range(H)]
colors = [[-2 for j in range(W)] for i in range(H)]
q = []
for i in range(H):
    A[i] = readline()[:-1]
    # print(A[i])
    for j,color in enumerate(A[i]):
        # print(j,color)
        colors[i][j] = 0 if color == '#' else -1
        if '#' == color:
            q.append([i,j,0])
            colors[i][j] = 0
# for i in colors:
#     print(i)
mx = 0
direction = [[1,0],[0,1],[-1,0],[0,-1]]

while len(q) > 0:
    # print(q)
    tmp = [y,x,op] = q.pop(0)
    mx = max(mx,op)
    if colors[y][x] >= 0 and mx > 0: continue
    for [dx,dy] in direction:
        ny,nx = y + dy , x + dx
        if  0 <= ny and ny < H and 0 <= nx and nx < W:
            if A[ny][nx] == '#' or colors[ny][nx] >= 0:
                continue
            q.append([ny,nx,op+1])
            colors[y][x] = op+1
print(mx)

Fixed submission:
from sys import stdin
from collections import deque
def main():
    readline = stdin.readline
    H,W = map(int,readline()[:-1].split())
    A = ['' for i in range(H)]
    visited = [[False] * W for i in range(H)]
    q = deque()
    for i in range(H):
        A[i] = readline()[:-1]
        # print(A[i])
        for j,color in enumerate(A[i]):
            if '#' == color:
                q.append([i,j,0])
                visited[i][j] = True
            # for i in visited:
            #     print(i)
    mx = 0
    direction = [[1,0],[0,1],[-1,0],[0,-1]]
    op = -1
    while len(q) > 0:
        # print(q)
        tmp = [y,x,op] = q.popleft()
        # print(tmp)
        mx = mx if mx > op else op
        for [dx,dy] in direction:
            ny,nx = y + dy , x + dx
            if  0 <= ny and ny < H and 0 <= nx and nx < W:
                if A[ny][nx] == '#' or visited[ny][nx] == True:
                    continue
                q.append([ny,nx,op+1])
                visited[ny][nx] = True
    print(op)

main()

Buggy python submission (verdict: Runtime Error):
from sys import stdin
readline = stdin.readline
H,W = map(int,input().split())
A = ['' for i in range(H)]
colors = [[-2 for j in range(W)] for i in range(H)]
q = []
for i in range(H):
    A[i] = list(readline())
    for j,color in enumerate(A[i]):
        colors[i][j] = 0 if color == '#' else -1
        if '#' == color:
            q.append([i,j,0])
            colors[i][j] = 0
# for i in colors:
#     print(i)
mx = 0
direction = [[1,0],[0,1],[-1,0],[0,-1]]

while len(q) > 0:
    # print(q)
    tmp = [y,x,op] = q.pop(0)
    mx = max(mx,op)
    if colors[y][x] >= 0 and mx > 0: continue
    for [dx,dy] in direction:
        ny,nx = y + dy , x + dx
        if  0 <= ny and ny < H and 0 <= nx and nx < W:
            if A[ny][nx] == '#' or colors[ny][nx] >= 0:
                continue
            q.append([ny,nx,op+1])
            colors[y][x] = op+1
print(mx)

Fixed submission:
from sys import stdin
from collections import deque
def main():
    readline = stdin.readline
    H,W = map(int,readline()[:-1].split())
    A = ['' for i in range(H)]
    visited = [[False] * W for i in range(H)]
    q = deque()
    for i in range(H):
        A[i] = readline()[:-1]
        # print(A[i])
        for j,color in enumerate(A[i]):
            if '#' == color:
                q.append([i,j,0])
                visited[i][j] = True
            # for i in visited:
            #     print(i)
    mx = 0
    direction = [[1,0],[0,1],[-1,0],[0,-1]]
    op = -1
    while len(q) > 0:
        # print(q)
        tmp = [y,x,op] = q.popleft()
        # print(tmp)
        mx = mx if mx > op else op
        for [dx,dy] in direction:
            ny,nx = y + dy , x + dx
            if  0 <= ny and ny < H and 0 <= nx and nx < W:
                if A[ny][nx] == '#' or visited[ny][nx] == True:
                    continue
                q.append([ny,nx,op+1])
                visited[ny][nx] = True
    print(op)

main()

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
A = ['' for i in range(H)]
colors = [[-2 for j in range(W)] for i in range(H)]
q = []
for i in range(H):
    A[i] = list(input())
    for j,color in enumerate(A[i]):
        colors[i][j] = 0 if color == '#' else -1
        if '#' == color:
            q.append([i,j,0])
            colors[i][j] = 0
# for i in colors:
#     print(i)
mx = 0
direction = [[1,0],[0,1],[-1,0],[0,-1]]

while len(q) > 0:
    # print(q)
    tmp = [y,x,op] = q.pop(0)
    mx = max(mx,op)
    if colors[y][x] >= 0 and mx > 0: continue
    for [dx,dy] in direction:
        ny,nx = y + dy , x + dx
        if  0 <= ny and ny < H and 0 <= nx and nx < W:
            if A[ny][nx] == '#' or colors[ny][nx] >= 0:
                continue
            q.append([ny,nx,op+1])
            colors[y][x] = op+1
print(mx)

Fixed submission:
from sys import stdin
from collections import deque
def main():
    readline = stdin.readline
    H,W = map(int,readline()[:-1].split())
    A = ['' for i in range(H)]
    visited = [[False] * W for i in range(H)]
    q = deque()
    for i in range(H):
        A[i] = readline()[:-1]
        # print(A[i])
        for j,color in enumerate(A[i]):
            if '#' == color:
                q.append([i,j,0])
                visited[i][j] = True
            # for i in visited:
            #     print(i)
    mx = 0
    direction = [[1,0],[0,1],[-1,0],[0,-1]]
    op = -1
    while len(q) > 0:
        # print(q)
        tmp = [y,x,op] = q.popleft()
        # print(tmp)
        mx = mx if mx > op else op
        for [dx,dy] in direction:
            ny,nx = y + dy , x + dx
            if  0 <= ny and ny < H and 0 <= nx and nx < W:
                if A[ny][nx] == '#' or visited[ny][nx] == True:
                    continue
                q.append([ny,nx,op+1])
                visited[ny][nx] = True
    print(op)

main()

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
A = ['' for i in range(H)]
colors = [[-2 for j in range(W)] for i in range(H)]
q = []
for i in range(H):
    A[i] = list(input())
    for j,color in enumerate(A[i]):
        colors[i][j] = 0 if color == '#' else -1
        if '#' == color:
            q.append([i,j,0])
            colors[i][j] = 0
# for i in colors:
#     print(i)
mx = 0
direction = [[1,0],[0,1],[-1,0],[0,-1]]

while len(q) > 0:
    # print(q)
    tmp = [y,x,op] = q.pop(0)
    mx = max(mx,op)
    if colors[y][x] >= 0 and mx > 0: continue
    for [dx,dy] in direction:
        ny,nx = y + dy , x + dx
        if  0 <= ny and ny < H and 0 <= nx and nx < W:
            if A[ny][nx] == '#' or colors[ny][nx] >= 0:
                continue
            q.append([ny,nx,op+1])
            colors[y][x] = op+1
print(mx)

Fixed submission:
from sys import stdin
from collections import deque
def main():
    readline = stdin.readline
    H,W = map(int,readline()[:-1].split())
    A = ['' for i in range(H)]
    visited = [[False] * W for i in range(H)]
    q = deque()
    for i in range(H):
        A[i] = readline()[:-1]
        # print(A[i])
        for j,color in enumerate(A[i]):
            if '#' == color:
                q.append([i,j,0])
                visited[i][j] = True
            # for i in visited:
            #     print(i)
    mx = 0
    direction = [[1,0],[0,1],[-1,0],[0,-1]]
    op = -1
    while len(q) > 0:
        # print(q)
        tmp = [y,x,op] = q.popleft()
        # print(tmp)
        mx = mx if mx > op else op
        for [dx,dy] in direction:
            ny,nx = y + dy , x + dx
            if  0 <= ny and ny < H and 0 <= nx and nx < W:
                if A[ny][nx] == '#' or visited[ny][nx] == True:
                    continue
                q.append([ny,nx,op+1])
                visited[ny][nx] = True
    print(op)

main()

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
A = ['' for i in range(H)]
colors = [[-2 for j in range(W)] for i in range(H)]
q = []
for i in range(H):
    A[i] = list(input())
    for j,color in enumerate(A[i]):
        colors[i][j] = 0 if color == '#' else -1
        if '#' == color:
            q.append([i,j,0])
# for i in colors:
#     print(i)
mx = 0
direction = [[1,0],[0,1],[-1,0],[0,-1]]
while len(q) > 0:
    # print(q)
    tmp = [y,x,op] = q.pop(0)
    mx = max(mx,op)
    if colors[y][x] >= 0 and mx > 0: continue
    colors[y][x] = op
    for [dx,dy] in direction:
        ny,nx = y + dy , x + dx
        if  0 <= ny and ny < H and 0 <= nx and nx < W:
            if A[ny][nx] == '#' or colors[ny][nx] >= 0:
                continue
            q.append([ny,nx,op+1])
print(mx)

Fixed submission:
from sys import stdin
from collections import deque
def main():
    readline = stdin.readline
    H,W = map(int,readline()[:-1].split())
    A = ['' for i in range(H)]
    visited = [[False] * W for i in range(H)]
    q = deque()
    for i in range(H):
        A[i] = readline()[:-1]
        # print(A[i])
        for j,color in enumerate(A[i]):
            if '#' == color:
                q.append([i,j,0])
                visited[i][j] = True
            # for i in visited:
            #     print(i)
    mx = 0
    direction = [[1,0],[0,1],[-1,0],[0,-1]]
    op = -1
    while len(q) > 0:
        # print(q)
        tmp = [y,x,op] = q.popleft()
        # print(tmp)
        mx = mx if mx > op else op
        for [dx,dy] in direction:
            ny,nx = y + dy , x + dx
            if  0 <= ny and ny < H and 0 <= nx and nx < W:
                if A[ny][nx] == '#' or visited[ny][nx] == True:
                    continue
                q.append([ny,nx,op+1])
                visited[ny][nx] = True
    print(op)

main()

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
A = ['' for i in range(H)]
colors = [[-2 for j in range(W)] for i in range(H)]
q = []
for i in range(H):
    A[i] = list(input())
    for j,color in enumerate(A[i]):
        colors[i][j] = 0 if color == '#' else -1
        if '#' == color:
            q.append([i,j,0])
# for i in colors:
#     print(i)
mx = 0
direction = [[1,0],[0,1],[-1,0],[0,-1]]
while len(q) > 0:
    # print(q)
    tmp = [y,x,op] = q.pop(0)
    mx = max(mx,op)
    if colors[y][x] > 0: continue
    colors[y][x] = op
    for [dx,dy] in direction:
        ny,nx = y + dy , x + dx
        if  0 <= ny and ny < H and 0 <= nx and nx < W:
            if A[ny][nx] == '#' or colors[ny][nx] >= 0:
                continue
            q.append([ny,nx,op+1])
print(mx)

Fixed submission:
from sys import stdin
from collections import deque
def main():
    readline = stdin.readline
    H,W = map(int,readline()[:-1].split())
    A = ['' for i in range(H)]
    visited = [[False] * W for i in range(H)]
    q = deque()
    for i in range(H):
        A[i] = readline()[:-1]
        # print(A[i])
        for j,color in enumerate(A[i]):
            if '#' == color:
                q.append([i,j,0])
                visited[i][j] = True
            # for i in visited:
            #     print(i)
    mx = 0
    direction = [[1,0],[0,1],[-1,0],[0,-1]]
    op = -1
    while len(q) > 0:
        # print(q)
        tmp = [y,x,op] = q.popleft()
        # print(tmp)
        mx = mx if mx > op else op
        for [dx,dy] in direction:
            ny,nx = y + dy , x + dx
            if  0 <= ny and ny < H and 0 <= nx and nx < W:
                if A[ny][nx] == '#' or visited[ny][nx] == True:
                    continue
                q.append([ny,nx,op+1])
                visited[ny][nx] = True
    print(op)

main()