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
import itertools
# import numpy as np
import time
import math
import heapq
from collections import defaultdict
sys.setrecursionlimit(10 ** 7)
 
INF = 10 ** 9 + 7
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

# map(int, input().split())

while True:
    W, H = map(int, input().split())
    if W == 0 and H == 0:
        break
    adj = defaultdict(list)
    for i in range(H):
        if i == 0:
            vertical = list(map(int, input().split()))
            for j in range(1, W):
                if vertical[j - 1] == 1:
                    continue
                adj[(i, j - 1)].append((i, j))
                adj[(i, j)].append((i, j - 1))
        else:
            horizontal = list(map(int, input().split()))
            for j in range(W):
                if horizontal[j] == 1:
                    continue
                adj[(i - 1, j)].append((i, j))
                adj[(i, j)].append((i - 1, j))

            vertical = list(map(int, input().split()))
            for j in range(1, W):
                if vertical[j - 1] == 1:
                    continue
                adj[(i, j - 1)].append((i, j))
                adj[(i, j)].append((i, j - 1))

    start = (0, 0)
    goal = (H - 1, W - 1)


    from collections import deque
    dist = [[-1] * W for _ in range(H)]
    q = deque([])
    sy, sx = start
    dist[sy][sx] = 1
    q.append(start)
    while len(q) > 0:
        v = q.popleft()
        y, x = v
        if v == goal:
            print(dist[y][x])
            break
        for u in adj[v]:
            ny, nx = u
            if dist[ny][nx] != -1:
                continue
            dist[ny][nx] = dist[y][x] + 1
            q.append(u)
    else:
        print(0)

Python: # Amazing Maze
from collections import deque

while True:
    w, h = map(int, input().split())
    if w == 0:
        break
    lr_walls = []
    ud_walls = []
    for i in range(2 * h - 1):
        wall = list(map(int, input().split()))
        if i % 2 == 0:
            lr_walls.append(wall)
        else:
            ud_walls.append(wall)
    checked = [[False] * w for _ in range(h)]
    checked[0][0] = True
    que = deque()
    que.append((1, 0, 0))
    while que:
        score, x, y = que.popleft()
        if (x, y) == (w - 1, h - 1):
            print(score)
            break

        if x < w - 1 and lr_walls[y][x] == 0 and not checked[y][x + 1]:
            checked[y][x + 1] = True
            que.append((score + 1, x + 1, y))

        if x > 0 and lr_walls[y][x - 1] == 0 and not checked[y][x - 1]:
            checked[y][x - 1] = True
            que.append((score + 1, x - 1, y))

        if y < h - 1 and ud_walls[y][x] == 0 and not checked[y + 1][x]:
            checked[y + 1][x] = True
            que.append((score + 1, x, y + 1))

        if y > 0 and ud_walls[y - 1][x] == 0 and not checked[y - 1][x]:
            checked[y - 1][x] = True
            que.append((score + 1, x, y - 1))
    else:
        print(0)

Python: while True:
    w, h = map(int, input().split())
    if w == 0:
        break
    row = []
    col = []
    for i in range(h-1):
        row.append(input().split())
        col.append(input().split())
    row.append(input().split())
    check_map = [[False for i in range(w)] for j in range(h)]
    search_list = [[0, 0, 1]]
    check_map[0][0] = True
    ok = False
    while len(search_list) > 0:
        x, y, step = search_list.pop(0)
        if x == w-1 and y == h-1:
            print(step)
            ok = True
            break
        # 左
        if x > 0:
            if row[y][x-1] == "0" and not check_map[y][x-1]:
                search_list.append([x-1, y, step+1])
                check_map[y][x-1] = True
        # 右
        if x < w-1:
            if row[y][x] == "0" and not check_map[y][x+1]:
                search_list.append([x+1, y, step+1])
                check_map[y][x+1] = True
        # 上
        if y > 0:
            if col[y-1][x] == "0" and not check_map[y-1][x]:
                search_list.append([x, y-1, step+1])
                check_map[y-1][x] = True
        # 下
        if y < h-1:
            if col[y][x] == "0" and not check_map[y+1][x]:
                search_list.append([x, y+1, step+1])
                check_map[y+1][x] = True
    if not ok:
        print(0)