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: d = [[0, -1],
     [0, 1],
     [-1, 0],
     [1, 0]]

INF = 1000000

tile = {"0":0,
        "1":1,
        " ":2}

def idx(i):
    return 2*i

output = []
while True:
    w, h = input().split()
    w = int(w)
    h = int(h)

    if w == 0:
        break

    maze = [[2 for i in range(2*w-1)] for j in range(2*h-1)]
    l = [[INF for i in range(w)] for j in range(h)]
    for j in range(2*h-1):
        row = input()
        for i in range(len(row)):
            maze[j][i] = tile[row[i]]
    
    queue = [(0, 0, 1)]
    while queue:
        x, y, count = queue.pop(0)

        for ud, rl in d:
            xxt = idx(x)+ud
            yyt = idx(y)+rl
            if xxt>=0 and xxt<w*2-1 and yyt>=0 and yyt<h*2-1:
                if maze[yyt][xxt] == 0:
                    xt = x+ud
                    yt = y+rl
                    if l[yt][xt] > count+1:
                        l[yt][xt] = count+1
                        queue.append((xt, yt, count+1))

    print(l)
    if l[h-1][w-1] == INF:
        output.append(0)
    else:
        output.append(l[h-1][w-1])

for i in output:
    print(i)

Python: cin = open(0).read().strip().split('\n')

from collections import deque

dx = [1, 0, -1, 0]
dy = [0, -1, 0, 1]

cnt = 0
while True:
    w,h = map(int, cin[cnt].split(' '))
    if w==0 and h==0: break

    var = [list(map(int, a.strip().split(' '))) for a in cin[cnt+1:cnt+1+(2*h-1):2]]
    hor = [list(map(int, a.split(' '))) for a in cin[cnt+2:cnt+2+(2*h-3):2]]

    q = deque()
    dist = [[0 for _ in range(w)] for _ in range(h)]
    dist[0][0] = 1
    q.append((0,0))
    while q:
        ph,pw = q.popleft()
        for dyi, dxi in zip(dy, dx):
            if ph+dyi>=h or ph+dyi<0: continue
            if pw+dxi>=w or pw+dxi<0: continue
            if dist[ph+dyi][pw+dxi] != 0: continue
            if (dyi==1 and hor[ph][pw] == 1) or (dyi==-1 and hor[ph+dyi][pw] == 1): continue
            if (dxi==1 and var[ph][pw] == 1) or (dxi==-1 and var[ph][pw+dxi] == 1): continue
            q.append((ph+dyi,pw+dxi))
            dist[ph+dyi][pw+dxi] = dist[ph][pw]+1
    print(dist[h-1][w-1])
    cnt += 2*h

Python: import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

from collections import deque
sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().rstrip()  # ignore trailing spaces

while True:
    w, h = na()
    if w == 0 and h == 0:
        break
    maze = [
        [0] * (w - 1) + [1], 
        *[na() if x % 2 != 0 else [1] + na() + [1] for x in range(2 * h - 1)],
        [1] + [0] * (w - 1)
    ]
    d = [[0] * w for _ in range(h)]
    que = deque()
    d[0][0] = 1
    que.append((0, 0))
    while que:
        y, x = que.popleft()
        t = y * 2 + 1
        t1 = t - 1
        t2 = t
        t3 = t + 1
        if maze[t1][x] == 0 and y-1 >= 0 and d[y-1][x] == 0:
            que.append((y-1, x))
            d[y-1][x] = d[y][x] + 1
        if maze[t2][x] == 0 and x-1 >= 0 and d[y][x-1] == 0:
            que.append((y, x-1))
            d[y][x-1] = d[y][x] + 1
        if maze[t2][x+1] == 0 and x+1 < w and d[y][x+1] == 0:
            que.append((y, x+1))
            d[y][x+1] = d[y][x] + 1
        if maze[t3][x] == 0 and y+1 < h and d[y+1][x] == 0:
            que.append((y+1, x))
            d[y+1][x] = d[y][x] + 1
    print(d[h-1][w-1])

Python: from collections import deque
while True:
    W,H = map(int, input().split())
    if W == 0: break
    es = [[] for i in range(W*H)]
    for y in range(H):
        walls_h = map(int, input().split())
        for x in range(W-1):
            if walls_h[x]: continue
            es[y*W + x].append(y*W + x+1)
            es[y*W + x+1].append(y*W + x)
        if y == H-1: break
        walls_v = map(int, input().split())
        for x in range(W):
            if walls_v[x]: continue
            es[y*W + x].append((y+1)*W + x)
            es[(y+1)*W + x].append(y*W + x)
    q = deque([0])
    dist = [0] * (W*H)
    dist[0] = 1
    while q:
        fr = q.popleft()
        for to in es[fr]:
            if dist[to] == 0:
                dist[to] = dist[fr] + 1
                q.append(to)
    print(dist[-1])