Go: package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		w, h := io.NextInt(), io.NextInt()
		if w == 0 {
			break
		}
		xWall := make([][]int, h)
		yWall := make([][]int, h)
		for i := 0; i < h; i++ {
			xWall[i], yWall[i] = make([]int, w), make([]int, w)
			for j := 0; j < w; j++ {
				xWall[i][j], yWall[i][j] = -1, -1
			}
		}
		for i := 0; i < h*2-1; i++ {
			if i%2 == 0 {
				for j := 0; j < w-1; j++ {
					xWall[i/2][j] = io.NextInt()
				}
			} else {
				for j := 0; j < w; j++ {
					yWall[i/2][j] = io.NextInt()
				}
			}
		}
		//io.Println(bfs(w, h, xWall, yWall))
		fmt.Println(bfs(w, h, xWall, yWall))
	}
}

type P struct {
	x, y int
}

func bfs(w, h int, x, y [][]int) int {
	d := make([][]int, h)
	for i := 0; i < h; i++ {
		d[i] = make([]int, w)
	}
	q := list.New()
	q.PushBack(P{0, 0})
	d[0][0] = 1

	for q.Len() != 0 {
		pos := q.Remove(q.Front()).(P)
		if pos.x == w-1 && pos.y == h-1 {
			break
		}
		if pos.x > 0 && x[pos.y][pos.x-1] == 0 && d[pos.y][pos.x-1] == 0 {
			d[pos.y][pos.x-1] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x - 1, pos.y})
		}
		if pos.x < w-1 && x[pos.y][pos.x] == 0 && d[pos.y][pos.x+1] == 0 {
			d[pos.y][pos.x+1] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x + 1, pos.y})
		}
		if pos.y > 0 && y[pos.y-1][pos.x] == 0 && d[pos.y-1][pos.x] == 0 {
			d[pos.y-1][pos.x] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x, pos.y - 1})
		}
		if pos.y < h-1 && y[pos.y][pos.x] == 0 && d[pos.y+1][pos.x] == 0 {
			d[pos.y+1][pos.x] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x, pos.y + 1})
		}
	}
	return d[h-1][w-1]
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

Python: from collections import deque
ans=[]
while True:
    w,h=map(int,input().split())
    if w==0 and h==0:
        break
    lr=[]
    ud=[]
    dist=[[-1]*(w+2) for _ in range(h+2)]
    dist[1][1]=1
    lr.append([1 for _ in range(w+1)])
    ud.append([1 for _ in range(w+2)])
    lr.append([1]+list(map(int,input().split()))+[1])
    for i in range(h-1):
        ud.append([1]+list(map(int,input().split()))+[1])
        lr.append([1]+list(map(int,input().split()))+[1])
    lr.append([1 for _ in range(w+1)])
    ud.append([1 for _ in range(w+2)])

    q=deque()
    q.append([1,1])
    while q:
        x,y=q.popleft()
        if 0<=y-1 and lr[x][y-1]==0:
            if dist[x][y-1]==-1 or dist[x][y-1]>dist[x][y]+1:
                q.append([x,y-1])
                dist[x][y-1]=dist[x][y]+1
        if y+1<=w+1 and lr[x][y]==0:
            if dist[x][y+1]==-1 or dist[x][y+1]>dist[x][y]+1:
                q.append([x,y+1])
                dist[x][y+1]=dist[x][y]+1
        if 0<=x-1 and ud[x-1][y]==0:
            if dist[x-1][y]==-1 or dist[x-1][y]>dist[x][y]+1:
                q.append([x-1,y])
                dist[x-1][y]=dist[x][y]+1
        if x+1<=h+1 and ud[x][y]==0:
            if dist[x+1][y]==-1 or dist[x+1][y]>dist[x][y]+1:
                q.append([x+1,y])
                dist[x+1][y]=dist[x][y]+1
    if dist[h][w]==-1:
        ans.append(0)
    else:
        ans.append(dist[h][w])
for i in ans:
    print(i)

Python: while True:
    m,n = map(int,input().split())
    sw = []
    bw = []
    if m == 0 and n == 0:
        break
    for i in range(2*n-1):
        if i % 2 == 0:
            sw.append(list(map(int,input().split())))
        else:
            bw.append(list(map(int,input().split())))
    flag = [[0 for i in range(m)] for j in range(n)]
    l = [(0,0,1)]
    res = 0
    while l:
        bf = l.pop(0)
        x,y,z = bf[0],bf[1],bf[2]
        if x == n-1 and y == m-1:
            res = z
            break
        flag[x][y] = 1
        if 1 <= x and bw[x-1][y] == 0 and flag[x-1][y] == 0:
            l.append((x-1,y,z+1))
        if y < m-1 and sw[x][y] == 0 and flag[x][y+1] == 0:
            l.append((x,y+1,z+1))
        if 1 <= y and sw[x][y-1] == 0 and flag[x][y-1] == 0:
            l.append((x,y-1,z+1))
        if x < n-1 and bw[x][y] == 0 and flag[x+1][y] == 0:
            l.append((x+1,y,z+1))
    print(res)

Python: #! cat input | python3 main.py
def solve():
    import heapq

    w, h = map(int, input().split())
    if w == 0 and h == 0:
        return False

    walls = []
    for i in range(h * 2 - 1):
        walls.append(list(map(int, input().split())))

    field = [[] for x in range(h * w)]

    for i in range(h):
        for j in range(w):
            f = j + i * w
            if j + 1 < len(walls[i]) and not walls[i*2][j]:
                    field[f].append(f + 1)
                    field[f + 1].append(f)
            if i + 1 < h and not walls[i*2 + 1][j]:
                field[f].append(f + w)
                field[f + w].append(f)
    # print(field)
    end = [False for x in range(w * h)]
    que = [(0, 0)]
    goal = h * w - 1
    results = []

    while que:
        tn, cost = que[0]
        del que[0]
        for n in field[tn]:
            if n == goal:
                results.append(cost)
                # return True
            elif not end[n]:
                end[n] = True
                que.append((n, cost + 1))

    print(min(results) + 2 if results else 0)
    return True

while solve(): pass

Python: from collections import deque
ans = []
while True:
    w, h = [int(x) for x in input().split()]
    if w == 0 and h == 0: break
    maze = [[1 for _ in range(2 * w + 1)] for _ in range(2 * h + 1)]
    for y in range(1, 2 * h):
        if y % 2 == 1:
            maze[y][2 : 2 * w : 2] = [int(x) for x in input().split()]
            maze[y][1 : 2 * w : 2] = [0] * w
        else:
            maze[y][1 : 2 * w : 2] = [int(x) for x in input().split()]

    que = deque([(1, 1, 0)])
    while que:
        y, x, d = que.popleft()
        if (y, x) == (2 * h - 1, 2 * w - 1):
            ans.append(d + 1)
            break
        for dy, dx in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
            wy = y + dy
            wx = x + dx
            if maze[wy][wx] == 1: continue # 壁
            ny = y + 2 * dy
            nx = x + 2 * dx
            if maze[ny][nx] == 1: continue # 訪問済み
            maze[ny][nx] = 1 # 訪問済みにする
            que.append((ny, nx, d + 1))
    else:
        ans.append(0)

for i in ans:
    print(i)