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: 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 = [(0,0,1)]
    while queue:
        p = queue.pop(0)
        x, y, z = p[0], p[1], p[2]
        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,z+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,z+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,z+1))
        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,z+1))
    print(node[w-1][h-1])

Python: def bfs(maze):
    d = [[0] * (w * 2 + 1) for i in range(h * 2 + 1)]
    d[1][1] = 1
    que = [(1, 1)]
    while que:
        x, y = que.pop(0)
        if x == 2 * w - 1 and y == 2 * h - 1:
            return d[y][x]
        for dx, dy in ((0, 1), (-1, 0), (0, -1), (1, 0)):
            mx, my = x + dx, y + dy
            nx, ny = mx + dx, my + dy
            if nx < 0 and w < nx and ny < 0 and h < ny:
                continue
            if maze[my][mx] == 0 and d[ny][nx] == 0:
                que.append((nx, ny))
                d[ny][nx] = d[y][x] + 1
    return 0

while True:
    w, h = map(int, input().split())
    maze = [[0] * (w * 2 + 1) for i in range(h * 2 + 1)]
    if w == h == 0:
        break
    for x in range(w * 2 + 1):
        maze[0][x] = maze[h * 2][x] = 1
    for y in range(h * 2 + 1):
        maze[y][0] = maze[y][w * 2] = 1

    for y in range(1, h * 2):
        a = [int(i) for i in input().split()]
        if y % 2 == 1:
            for x in range(w - 1):
                maze[y][2 * x + 2] = a[x]
        else:
            for x in range(w):
                maze[y][2 * x + 1] = a[x]

    print(bfs(maze))

Python: def solve():
    import sys
    file_input = sys.stdin
    
    while True:
        w, h = map(int, file_input.readline().split())
        if w == 0 and h == 0:
            break
        
        width = 2 * w + 1
        
        maze = '1' * width
        line = file_input.readline()
        maze += '1' + line.rstrip() + ' 1'
        for _ in range(h - 1):
            line = file_input.readline()
            maze += '1' + line.rstrip() + '1'
            line = file_input.readline()
            maze += '1' + line.rstrip() + ' 1'
        maze += '1' * width
        
        start = width + 1
        goal = len(maze) - width - 2
        
        from collections import deque
        forward_q = deque()
        forward_q.append(start)
        reverse_q = deque()
        reverse_q.append(goal)
        
        forward_rec = [None] * (goal + 1)
        forward_rec[start] = 1
        reverse_rec = [None] * (goal + 1)
        reverse_rec[goal] = 1
        
        adj_move = (1, -1, width, -width)
        
        while forward_q and reverse_q:
            fp = forward_q.popleft()
            fp_len = forward_rec[fp]
            rp = reverse_q.popleft()
            rp_len = reverse_rec[rp]
            
            for move in adj_move:
                wall = maze[fp + move]
                if wall == '0':
                    next_place = fp + move * 2
                    if forward_rec[next_place] == None:
                        if reverse_rec[next_place]:
                            print(fp_len + reverse_rec[next_place])
                            break
                        forward_q.append(next_place)
                        forward_rec[next_place] = fp_len + 1
                wall = maze[rp + move]
                if wall == '0':
                    next_place = rp + move * 2
                    if reverse_rec[next_place] == None:
                        if forward_rec[next_place]:
                            print(rp_len + forward_rec[next_place])
                            break
                        reverse_q.append(next_place)
                        reverse_rec[next_place] = rp_len + 1
            else:
                continue
            break
        else:
            print(0)

solve()