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

def solve():
    H, W = map(int, input().split())

    l = []
    for _ in range(H):
        l.append([0 if s=="." else 1 for s in input()])

    ans = 0

    for sh,sw,gh,gw in product(range(H),range(W),range(H),range(W)):
        if gw==sw and gh==sh:
            continue
        if l[gh][gw] or l[sh][sw]:
            continue

        q = deque([(sh, sw)])
        dist = [[10**12]*W for _ in range(H)]
        dist[sh][sw] = 0
        while q:
            h, w = q.popleft()
            for h1, w1 in [(h+1, w), (h, w+1), (h-1, w), (h, w-1)]:
                if not (0<=h1<H and 0<=w1<W):continue
                if l[h1][w1]:continue
                if dist[h1][w1] > dist[h][w] + 1:
                    dist[h1][w1] = dist[h][w] + 1
                    q.append((h1, w1))
        ans = max(ans, dist[gh][gw])
        
    print(ans)

solve()

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

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

def solve():
    H, W = map(int, input().split())

    l = []
    for _ in range(H):
        l.append([0 if s=="." else 1 for s in input()])

    ans = 0
    for sh in range(H):
        for sw in range(W):
            for gh in range(H):
                for gw in range(W):
                    if gw==sw and gh==sh:
                        continue
                    if l[gh][gw] or l[sh][sw]:
                        continue

                    q = deque([(sh, sw)])
                    dist = [[10**12]*W for _ in range(H)]
                    dist[sh][sw] = 0
                    while q:
                        h, w = q.popleft()
                        for h1, w1 in [(h+1, w), (h, w+1), (h-1, w), (h, w-1)]:
                            if not (0<=h1<H and 0<=w1<W):continue
                            if l[h1][w1]:continue
                            if dist[h1][w1] > dist[h][w] + 1:
                                dist[h1][w1] = dist[h][w] + 1
                                q.append((h1, w1))
                    ans = max(ans, dist[gh][gw])
    print(ans)

solve()

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

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

def solve():
    H, W = map(int, input().split())

    l = []
    for _ in range(H):
        l.append([0 if s=="." else 1 for s in input()])

    def dfs(sh, sw, gh, gw):
        q = deque([(sh, sw)])
        dist = [[10**12]*W for _ in range(H)]
        dist[sh][sw] = 0
        while q:
            h, w = q.popleft()
            for h1, w1 in [(h+1, w), (h, w+1), (h-1, w), (h, w-1)]:
                if not (0<=h1<H and 0<=w1<W):continue
                if l[h1][w1]:continue
                if dist[h1][w1] > dist[h][w] + 1:
                    dist[h1][w1] = dist[h][w] + 1
                    q.append((h1, w1))
        return dist[gh][gw]

    ans = 0
    for sh in range(H):
        for sw in range(W):
            for gh in range(H):
                for gw in range(W):
                    if gw==sw and gh==sh:
                        continue
                    if l[gh][gw] or l[sh][sw]:
                        continue
                    ans = max(ans, dfs(sh, sw, gh, gw))
    print(ans)

solve()

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())

l = []
for _ in range(H):
    l.append([0 if s=="." else 1 for s in input()])

def dfs(sh, sw, gh, gw):
    q = deque([(sh, sw)])
    dist = [[10**12]*W for _ in range(H)]
    dist[sh][sw] = 0
    while q:
        h, w = q.popleft()
        for h1, w1 in [(h+1, w), (h, w+1), (h-1, w), (h, w-1)]:
            if not (0<=h1<H and 0<=w1<W):continue
            if l[h1][w1]:continue
            if dist[h1][w1] > dist[h][w] + 1:
                dist[h1][w1] = dist[h][w] + 1
                q.append((h1, w1))
    return dist[gh][gw]

ans = 0
for sh in range(H):
    for sw in range(W):
        for gh in range(H):
            for gw in range(W):
                if gw==sw and gh==sh:
                    continue
                if l[gh][gw] or l[sh][sw]:
                    continue
                ans = max(ans, dfs(sh, sw, gh, gw))
print(ans)


Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = float("inf")

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
m = [input() for _ in range(H)]
inf = float("inf")

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Runtime Error):
from collections import deque
import sys
import numpy as np

input = sys.stdin.readline
H, W = map(int, input().split())

maze = np.zeros((H, W), dtype='int')


for y in range(H):
    for x, s in enumerate(input()):
        if s=="#":
            maze[y][x] = 1


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = np.zeros_like(maze, dtype='int') 

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = 1
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and visited[cy][cx] == 0 and maze[cy][cx] == 0:
                queue.append((cx, cy, cost + 1))
    
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == 0:
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
import numpy as np

input = sys.stdin.readline
H, W = map(int, input().split())

maze = np.zeros((H, W), dtype='int')


for y in range(H):
    for x, s in enumerate(input()):
        if s=="#":
            maze[y][x] = 1


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = np.zeros_like(maze, dtype='int') 

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = 1
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and visited[cy][cx] == 0 and maze[cy][cx] == 0:
                queue.append((cx, cy, cost + 1))
    
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == 0:
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

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

input = sys.stdin.readline
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = [[False]*W for _ in range(H)]

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = True
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not visited[cy][cx] and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = [[False]*W for _ in range(H)]

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = True
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not visited[cy][cx] and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)


Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = [[False]*W for _ in range(H)]

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = True
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not visited[cy][cx] and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [input() for _ in range(H)]


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = [[False]*W for _ in range(H)]

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = True
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not visited[cy][cx] and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [input() for _ in range(H)]


def bfs(x, y):
    queue = deque([(x, y, 0)])
    visited = [[False]*W for _ in range(H)]

    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited[py][px] = True
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not visited[cy][cx] and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [input() for _ in range(H)]


def bfs(x, y):
    visited, queue = [], deque([(x, y, 0)])
    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not (cx, cy) in visited and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)


Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], deque([(x, y, 0)])
    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not (cx, cy) in visited and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == ".":
            ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], deque([(x, y, 0)])
    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not (cx, cy) in visited and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], deque([(x, y, 0)])
    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if 0 <= cx < W and 0 <= cy < H and not (cx, cy) in visited and maze[cy][cx] == ".":
                queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

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

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


def bfs(x, y):
    visited, queue = [], deque([(x, y, 0)])
    max_cost = 0
    while queue:
        px, py, cost = queue.popleft()
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if not (0 <= cx < W and 0 <= cy < H):
                continue
            if (cx, cy) in visited:
                continue
            if maze[cy][cx] == "#":
                continue
            queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], [(x, y, 0)]
    max_cost = 0
    while queue:
        px, py, cost = queue.pop(0)
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if not (0 <= cx < W and 0 <= cy < H):
                continue
            if (cx, cy) in visited:
                continue
            if maze[cy][cx] == "#":
                continue
            queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], [(x, y, 0)]
    max_cost = 0
    while queue:
        px, py, cost = queue.pop(0)
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if not (0 <= cx < W and 0 <= cy < H):
                continue
            if (cx, cy) in visited:
                continue
            if maze[cy][cx] == "#":
                continue
            queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], [(x, y, 0)]
    max_cost = 0
    while queue:
        px, py, cost = queue.pop(0)
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if not (0 <= cx < W and 0 <= cy < H):
                continue
            if maze[cy][cx] == "#":
                continue
            if (cx, cy) in visited:
                continue
            queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
maze = [list(input()) for _ in range(H)]


def bfs(x, y):
    visited, queue = [], [(x, y, 0)]
    max_cost = 0
    while queue:
        px, py, cost = queue.pop(0)
        max_cost = max(max_cost, cost)

        candidate = ((px + 1, py), (px - 1, py), (px, py + 1), (px, py - 1))
        visited.append((px, py))
        for cx, cy in candidate:
            if not (0 <= cx < W and 0 <= cy < H):
                continue
            if maze[cy][cx] == "#":
                continue
            if (cx, cy) in visited:
                continue
            queue.append((cx, cy, cost + 1))
    return max_cost


ans = 0
for y in range(H):
    for x in range(W):
        if maze[y][x] == "#":
            continue
        ans = max(ans, bfs(x, y))

print(ans)

Fixed submission:
H, W = map(int, input().split())
m = [list(input()) for _ in range(H)]
inf = 10**3

V = H*W
maze = [[inf]*V for _ in range(V)]

for i in range(V):
    maze[i][i] = 0

for py in range(H):
    for px in range(W):
        if m[py][px] == "#":
            continue
        candidate = [(px+1, py), (px-1, py), (px, py+1), (px, py-1)]
        for x, y in candidate:
            if not (0<=x<W and 0<=y<H):continue
            if m[y][x] == "#":
                continue
            maze[W*py+px][W*y+x] = 1

for k in range(V):
    for i in range(V):
        for j in range(V):
            maze[i][j] = min(maze[i][j], maze[i][k]+maze[k][j])

print(max([j for i in maze for j in i if j!=inf]))