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: import sys
from collections import deque
input = sys.stdin.readline
sys.setrecursionlimit(2 * 10**6)


def inpl():
    return list(map(int, input().split()))


dhl = [-1, 1]
dw = [(0, 1), (0, -1)]


def getNeighbor(h, w):
    # print(h, w)
    if h < H - 1 and vertical[h][w] == 0:
        yield (h + 1, w)
    if h > 0 and vertical[h - 1][w] == 0:
        yield (h - 1, w)
    if w > 0 and horizon[h][w - 1] == 0:
        yield (h, w - 1)
    if w < W - 1 and horizon[h][w] == 0:
        yield (h, w + 1)


def solve():
    mp = [[0] * W for _ in range(H)]
    Q = deque()
    Q.append((0, 0))
    while Q:
        # print(Q)
        nh, nw = Q.popleft()
        for h, w in getNeighbor(nh, nw):
            if mp[h][w] == 0:
                mp[h][w] = mp[nh][nw] + 1
                Q.append((h, w))

    return 0 if mp[H - 1][W - 1] == 0 else mp[H - 1][W - 1] + 1


ans = []
while True:
    W, H = inpl()
    if W == H == 0:
        break
    horizon = []
    vertical = []
    for _ in range(H - 1):
        horizon.append(inpl())
        vertical.append(inpl())
    horizon.append(inpl())
    ans.append(solve())

for a in ans:
    print(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))

    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: def main():
    w,h=map(int,input().split())
    if w==0 and h==0 : exit()
    #接続リストを作る
    con=[[[] for j in range(w)] for _ in range(h)]

    token=0 
    for i in range(2*h-1):
        lst=input().split()
        if token==0 :
            for j,x in enumerate(lst):
                if x=="0":
                    con[i//2][j].append((i//2,j+1))
                    con[i//2][j+1].append((i//2,j))
            token=1
        else :
            for j,x in enumerate(lst):
                if x=="0" :
                    con[(i+1)//2][j].append(((i-1)//2,j))
                    con[(i-1)//2][j].append(((i+1)//2,j))
            token=0
        #print(i,con)
    
    seen=[[-1]*w for _ in range(h)]
    seen[0][0]=1
    bfs_new=[(0,0)]
    token=1
    
    while bfs_new:
        bfs_old=bfs_new[:]
        bfs_new=[]
        token+=1
        for ax,ay in bfs_old:
            for bx,by in con[ax][ay]:
                if seen[bx][by]>=0 : continue
                seen[bx][by]=token
                bfs_new.append((bx,by))
    
    if seen[h-1][w-1]==-1 : print(0)
    else : print(seen[h-1][w-1])

while 1:
    main()

Python: while True:
    w, h = map(int, input().split())
    if w == 0: break
    goal = (w,h)
    vart = []
    hori = []
    for i in range(2*h-1):
        if i % 2 == 0:
            vart.append(list(map(int, input().split())))
        else:
            hori.append(list(map(int, input().split())))
    node = [[0 for i in range(h)] for i in range(w)]
    queue = [(0,0)]
    while queue:
        p = queue.pop(0)
        x, y = p[0], p[1]
        node[x][y] += 1
        if y-1 >= 0 and hori[y-1][x] == 0 and node[x][y-1] == 0:
            node[x][y-1] = node[x][y]
            queue.append((x,y-1))
        if y+1 < h and hori[y][x] == 0 and node[x][y+1] == 0:
            node[x][y+1] = node[x][y]
            queue.append((x,y+1))
        if x-1 >= 0 and vart[y][x-1] == 0 and node[x-1][y] == 0:
            node[x-1][y] = node[x][y]
            queue.append((x-1,y))
        if x+1 < w and vart[y][x] == 0 and node[x+1][y] == 0:
            node[x+1][y] = node[x][y]
            queue.append((x+1,y))
    print(node[goal[0]-1][goal[1]-1])