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 math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools

sys.setrecursionlimit(10**7)
inf = 10**20
eps = 1.0 / 10**10
mod = 998244353

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
def pf(s): return print(s, flush=True)


class Dijkstra():
    def __init__(self):
        self.e = collections.defaultdict(list)

    def add(self, u, v, d):
        self.e[u].append([v,d])
        self.e[v].append([u,d])

    def delete(self, u, v):
        self.e[u] = [_ for _ in self.e[u] if _[0] != v]
        self.e[v] = [_ for _ in self.e[v] if _[0] != u]

    def search(self, s, t):
        d = collections.defaultdict(lambda: inf)
        d[s] = 0
        q = []
        heapq.heappush(q, (0, s))
        v = collections.defaultdict(bool)
        while len(q):
            k, u = heapq.heappop(q)
            if v[u]:
                continue
            if u == t:
                return d[t]
            v[u] = True

            for uv, ud in self.e[u]:
                if v[uv]:
                    continue
                vd = k + ud
                if d[uv] > vd:
                    d[uv] = vd
                    heapq.heappush(q, (vd, uv))

        return None

def main():
    rr = []

    while True:
        w,h = LI()
        if h == 0 and w == 0:
            break

        a = [LI() for _ in range(h*2-1)]

        dk = Dijkstra()
        for i in range(h):
            for j in range(w-1):
                if a[i*2][j] == 0:
                    dk.add((i,j), (i,j+1), 1)
        for i in range(h-1):
            for j in range(w):
                if a[i*2+1][j] == 0:
                    dk.add((i,j), (i+1,j), 1)
        r = dk.search((0,0),(h-1,w-1))
        if r:
            rr.append(r+1)
        else:
            rr.append(0)

    return '\n'.join(map(str, rr))


print(main())

Python: from collections import deque

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


def bfs(w, h, m):
    cost = [[-1 for _ in range(w + (w - 1))] for _ in range(h + (h - 1))]
    # print(cost)
    que = deque()
    que.append([0, 0])
    cost[0][0] = 2
    while not len(que) == 0:
        p = que.popleft()
        # print((w+(w-2)), (h+(h-2)))
        if p[0] == 2 * h - 2 and p[1] == 2 * w - 2:
            return cost[p[0]][p[1]] // 2
        for i in range(4):
            nx = p[0] + dx[i]
            ny = p[1] + dy[i]
            # print(nx, ny, 2 * h - 1, 2 * w - 1)
            if nx < 0 or ny < 0 or nx >= 2 * h - 1 or ny >= 2 * w - 1:
                # print(cost[nx][ny])
                continue
            if m[nx][ny] == -1:
                continue
            if not cost[nx][ny] == -1:
                continue
            # print(p[0], p[1], cost)
            cost[nx][ny] = cost[p[0]][p[1]] + 1
            # print(cost[nx][ny], len(que))
            que.append([nx, ny])
        # print(*cost, sep="\n")
        # print("---------------------")
    return 0


if __name__ == "__main__":
    while True:
        W, H = map(int, input().split())
        if W == 0 and H == 0:
            break
        meizu = [[0 for _ in range(W + (W - 1))] for _ in range(H + (H - 1))]
        for i in range(2 * H - 1):
            kabe = list(map(int, input().split()))
            tmp = 0
            if i % 2 == 0:
                for j in range(len(meizu[i])):
                    if j % 2 == 1:
                        if kabe[tmp] == 1:
                            meizu[i][j] = -1
                        tmp += 1
            else:
                for j in range(len(meizu[i])):
                    if j % 2 == 0:
                        if kabe[tmp] == 1:
                            meizu[i][j] = -1
                        tmp += 1
        for i in range(len(meizu)):
            for j in range(len(meizu[i])):
                if i % 2 == 1 and j % 2 == 1:
                    meizu[i][j] = -1
        # print(meizu)
        print(bfs(W, H, meizu))