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: 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)
        
        def shortest_path_len():
            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]:
                                return fp_len + reverse_rec[next_place]
                            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]:
                                return rp_len + forward_rec[next_place]
                            reverse_q.append(next_place)
                            reverse_rec[next_place] = rp_len + 1
            return 0
        
        print(shortest_path_len())

solve()

Python: import collections,sys
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
while 1:
    w,h = LI()
    if w==h==0:
        break
    hwall,wwall = [],[]
    for i in range(2*h-1):
        hwall.append(LI()) if i%2==0 else wwall.append(LI())
    dhdw = [[-1,0],[1,0],[0,-1],[0,1]]
    min_dist = [[-1]*w for _ in range(h)]
    seen = [[0]*w for _ in range(h)]
    queue = collections.deque() #位置[行,列]を入れておく
    def bfs():
        seen[0][0] = 1
        queue.append([0,0])
        min_dist[0][0] = 1
        while queue:
            qh,qw = queue.popleft()
            for dh,dw in dhdw:
                nh,nw = qh+dh,qw+dw
                if not(0<=nh<=h-1) or not(0<=nw<=w-1) or seen[nh][nw]:
                    continue
                if (dh==-1 and wwall[nh][nw]==1) or (dh==1 and wwall[nh-1][nw]==1):
                    continue
                if (dw==-1 and hwall[nh][nw]==1) or (dw==1 and hwall[nh][nw-1]==1):
                    continue
                if [nh,nw]==[h-1,w-1]:
                    return min_dist[qh][qw]+1
                seen[nh][nw] = 1
                queue.append([nh,nw])
                min_dist[nh][nw] = min_dist[qh][qw]+1
    print(bfs() or 0)