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: from collections import deque

while True:
    a,b = map(int,input().split())
    if a == b == 0:
        break
    map_list = []
    map_list.append([1 for i in range(2 * a + 1)])
    for i in range(2 * b - 1):
        
        lis_c = list(map(int,input().split()))
        if i % 2 == 0:
            row = [2 for i in range(2 * a - 1)]
            for j in range(len(lis_c)):
                row[2 * j + 1] = lis_c[j]
            
        else:
            row = [1 for i in range(2 * a - 1)]
            for j in range(len(lis_c)):
                row[2 * j] = lis_c[j]
        row.append(1)
        row.insert(0,1)
        map_list.append(row)
    map_list.append([1 for i in range(2 * a + 1)])


    
    time = 0
    M_dic = {}
    M_que = deque([])
    M_que.append([time,[1,1]])
    M_dic[(1,1)] = time
    while True:
        now_list = M_que.popleft()
        now_time = now_list[0]

        now_pos = now_list[1]
        if now_pos == [2 * b - 1,2 * a - 1]:
            print(now_time + 1)
            break
            
        if map_list[now_pos[0] + 1][now_pos[1]] == 0:
            if not (now_pos[0] + 2,now_pos[1]) in M_dic:
                M_dic[(now_pos[0] + 2,now_pos[1])] = now_time + 1
                M_que.append([now_time + 1, [now_pos[0] + 2,now_pos[1]]])
   
        if map_list[now_pos[0]][now_pos[1] + 1] == 0:
            if not (now_pos[0],now_pos[1] + 2) in M_dic:
                M_dic[(now_pos[0],now_pos[1] + 2)] = now_time + 1
                M_que.append([now_time + 1, [now_pos[0],now_pos[1] + 2]])
                
        if map_list[now_pos[0] - 1][now_pos[1]] == 0:
            if not (now_pos[0] - 2,now_pos[1]) in M_dic:
                M_dic[(now_pos[0] - 2,now_pos[1])] = now_time + 1
                M_que.append([now_time + 1, [now_pos[0] - 2,now_pos[1]]])
   
        if map_list[now_pos[0]][now_pos[1] - 1] == 0:
            if not (now_pos[0],now_pos[1] - 2) in M_dic:
                M_dic[(now_pos[0],now_pos[1] - 2)] = now_time + 1
                M_que.append([now_time + 1, [now_pos[0],now_pos[1] - 2]])
                
        if len(M_que) == 0:
            print(0)
            break

Python: # coding: utf-8

import sys
from collections import deque

if __name__ == '__main__':
    while True:
        m,n = map(int,input().split())
        sw = []
        bw = []
        if m == 0 and n == 0:
            break
        for i in range(2*n-1):
            if i % 2 == 0:
                sw.append(list(map(int,input().split())))
            else:
                bw.append(list(map(int,input().split())))
        flag = [[0 for i in range(m)] for j in range(n)]
        l = []
        l.append([0,0,1])
        res = 0
        while len(l) != 0:
            bf = l[0]
            l.pop(0)
            if bf[0] == n-1 and bf[1] == m-1:
                res = bf[2]
                break
            flag[bf[0]][bf[1]] = 1
            if 1 <= bf[0] and bw[bf[0]-1][bf[1]] == 0 and flag[bf[0]-1][bf[1]] == 0:
                l.append([bf[0]-1,bf[1],bf[2]+1])
            if bf[1] < m-1 and sw[bf[0]][bf[1]] == 0 and flag[bf[0]][bf[1]+1] == 0:
                l.append([bf[0],bf[1]+1,bf[2]+1])
            if 1 <= bf[1] and sw[bf[0]][bf[1]-1] == 0 and flag[bf[0]][bf[1]-1] == 0:
                l.append([bf[0],bf[1]-1,bf[2]+1])
            if bf[0] < n-1 and bw[bf[0]][bf[1]] == 0 and flag[bf[0]+1][bf[1]] == 0:
                l.append([bf[0]+1,bf[1],bf[2]+1])
        print(res)

Python: def bfs(maze):
    d = [[0] * 65 for i in range(65)]
    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] * 65 for i in range(65)]
    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))