Buggy python submission (verdict: Runtime Error):
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

Fixed submission:
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

Fixed submission:
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]
 
def bfs(i, j):
    D = [[INF] * W for i in range(H)]
    que = deque()
    que.append([i, j])
    D[i][j] = 0
    
    while que != []:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
            elif 0 <= nx < H and 0 <= ny < W and A[nx][ny] == '#':
                D[nx][ny] = D[p[0]][p[1]] + 1
                return D[nx][ny]
              
ans = 0
for i in range(H):
    for j in range(W):
        if A[i][j] == '.':
            tmp = bfs(i, j)
            ans = max(ans, tmp)
            
print(ans)

Fixed submission:
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]
 
def bfs(i, j):
    D = [[INF] * W for i in range(H)]
    que = deque()
    que.append([i, j])
    D[i][j] = 0
    
    while que != []:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
            elif 0 <= nx < H and 0 <= ny < W and A[nx][ny] == '#':
                D[nx][ny] = D[p[0]][p[1]] + 1
                return D[nx][ny]
              
ans = 0
for i in range(H):
    for j in range(W):
        if A[i][j] == '.':
            tmp = bfs(i, j)
            ans = max(ans, tmp)
            
print(ans)

Fixed submission:
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]
 
def bfs(i, j):
    D = [[INF] * W for i in range(H)]
    que = deque()
    que.append([i, j])
    D[i][j] = 0
    
    while que != []:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
            elif 0 <= nx < H and 0 <= ny < W and A[nx][ny] == '#':
                D[nx][ny] = D[p[0]][p[1]] + 1
                return D[nx][ny]
 
ans = 0
for i in range(H):
    for j in range(W):
        if A[i][j] == '.':
            tmp = bfs(i, j)
            ans = max(ans, tmp)
            
print(ans)

Fixed submission:
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)

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

H, W = map(int, input().split())
A = [list(input()) for i in range(H)]

INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]

def bfs(i, j):
    D = [[INF] * W for i in range(H)]
    que = deque()
    que.append([i, j])
    D[i][j] = 0
    
    while que != []:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
            elif 0 <= nx < H and 0 <= ny < W and A[nx][ny] == '#':
                D[nx][ny] = D[p[0]][p[1]] + 1
                return D[nx][ny]

ans = 0
for i in range(H):
    for j in range(W):
        if A[i][j] == '.':
            tmp = bfs(i, j)
            ans = max(ans, tmp)
            
print(ans)

Fixed submission:
from collections import deque
 
H, W = map(int, input().split())
A = [list(input()) for i in range(H)]
 
que = deque()
INF = float('inf')
dx = [1, 0, -1, 0]
dy = [0, 1, 0 , -1]            
D = [[INF] * W for i in range(H)]

for i in range(H):
    for j in range(W):
        if A[i][j] == '#':
            que.append([i, j])
            D[i][j] = 0
                       
def bfs():
    while len(que) != 0:
        p = que.popleft()
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            if 0 <= nx < H and 0 <= ny < W and A[nx][ny] != '#' and D[nx][ny] == INF:
                que.append([nx, ny])
                D[nx][ny] = D[p[0]][p[1]] + 1
    
bfs()

ans = 0
for i in range(H):
    for j in range(W):
        tmp = D[i][j]
        ans = max(ans, tmp)
        
print(ans)