Buggy python submission (verdict: Runtime Error):
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if s[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

Buggy python submission (verdict: Runtime Error):
import sys

H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

# たどりつけない場合
if s[gy - 1][gx] == "#" and s[gy][gx - 1] == "#":
    print(-1)
    sys.exit()

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break

print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

Buggy python submission (verdict: Runtime Error):
import sys

H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

# たどりつけない場合
if s[gy - 1][gx] == "#" and s[gy][gx - 1] == "#":
    print(-1)
    sys.exit()

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#" and visited[ny][nx] > visited[ty][tx] + 1:
            visited[ny][nx] = visited[ty][tx] + 1
            q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break

print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

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

H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

# たどりつけない場合
if s[gy - 1][gx] == "#" and s[gy][gx - 1] == "#":
    print(-1)
    sys.exit()

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
counter = 0
while True:
    nq = []
    counter += 1
    for ty, tx in q:
        if [gy, gx] in q:
            break
        for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            ny, nx = ty + dy, tx + dx
            if 0 <= ny < H and 0 <= nx < W and s[ny][nx] == "." and visited[ny][nx] > counter:
                visited[ny][nx] = counter
                nq.append([ny, nx])
                if ny == gy and nx == gx:
                    break
    q = nq
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break

print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

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

H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

# たどりつけない場合
if s[gy - 1][gx] == "#" and s[gy][gx - 1] == "#":
    print(-1)
    sys.exit()

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while True:
    nq = []
    for ty, tx in q:
        if [gy, gx] in q:
            break
        for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            ny, nx = ty + dy, tx + dx
            if 0 <= ny < H and 0 <= nx < W and s[ny][nx] == "." and visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                nq.append([ny, nx])
                if ny == gy and nx == gx:
                    break
    q = nq
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break

print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

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

H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

# たどりつけない場合
if s[gy - 1][gx] == "#" and s[gy][gx - 1] == "#":
    print(-1)
    sys.exit()

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while True:
    nq = []
    for ty, tx in q:
        for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            ny, nx = ty + dy, tx + dx
            if 0 <= ny < H and 0 <= nx < W and s[ny][nx] == "." and visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                nq.append([ny, nx])
    q = nq
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break

print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)

Buggy python submission (verdict: Runtime Error):
import sys

H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

# たどりつけない場合
if s[gy - 1][gx] == "#" and s[gy][gx - 1] == "#":
    print(-1)
    sys.quit()

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while True:
    nq = []
    for ty, tx in q:
        for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            ny, nx = ty + dy, tx + dx
            if 0 <= ny < H and 0 <= nx < W and s[ny][nx] == "." and visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                nq.append([ny, nx])
    q = nq
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break

print(nw - temp - 1)

Fixed submission:
H, W = map(int, input().split())
s = []
nb = 0
for _ in range(H):
    s.append(list(input()))
    nb += s[-1].count("#")

nw = H * W - nb

sy, sx = 0, 0
gy, gx = H - 1, W - 1

q = [[sy, sx]]
visited = [[int(1e10)]*W for _ in range(H)]
visited[sy][sx] = 0
while q:
    ty, tx = q.pop(0)
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        ny, nx = ty + dy, tx + dx
        if 0 <= ny < H and 0 <= nx < W and s[ny][nx] != "#":
            if visited[ny][nx] > visited[ty][tx] + 1:
                visited[ny][nx] = visited[ty][tx] + 1
                q.append([ny, nx])
    if [gy, gx] in q:
        temp = visited[gy][gx]
        break
if visited[gy][gx] == int(1e10):
    print(-1)
else: print(nw - temp - 1)