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
from collections import defaultdict


while True:
    W,H = map(int,input().split())
    if W==0 and H==0:
        break

    grid = defaultdict()

    raw_grid = []

    for _ in range(0,2*H-1):
        raw_grid.append(list(map(int, input().split())))

    for i in range(W):                           # 縦移動
        for j in range(1, 2 * H - 2, 2):
            p = int(i+W*(j-1)/2)
            q = int(i+W*(j+1)/2)
            grid[(p, q)] = raw_grid[j][i]
            grid[(q, p)] = grid[(p, q)]

    for j in range(0,2*H-1,2):                  # 横移動
        for i in range(W-1):
            p = int(i+W*j/2)
            q = int(i+1+W*j/2)
            grid[(p, q)] = raw_grid[j][i]
            grid[(q, p)] = grid[(p, q)]

    for i in range(W):              # 縦の壁
        grid[(i,i-W)] = 1
        grid[(i-W,i)] = 1
        grid[(W*(H-1)+i,W*H+i )] = 1
        grid[(W*H+i, W*(H-1)+i)] = 1
    for j in range(H):              # 横の壁
        grid[(W*j,W*j-1)] = 1
        grid[(W*j-1,W*j)] = 1


    move = [1,-1, W, -W]
    start = 0

    se = set([start]) # 到達可能

    next_set = deque()
    next_set.append((start, 0))
    flg =False

    while next_set:    # q = [] になったら止める
        p, t = next_set.popleft()     # 要素を消去して、消去した要素を出力
        for dx in move:
            q = p + dx
            if (q < 0 or q > W * H - 1):
                continue
            if grid[(p, q)] == 1 or q in se:
                continue
            if q == W*H-1:
                print(t + 2)
                flg = True
                break
            se.add(q)   # すでに到達した道を記憶
            next_set.append((q, t + 1))     # yに移動
        if flg:
            break
    if not flg:
        print(0)

Python: def solve():
    w, h = map(int, input().split())
    if w == 0 and h == 0:
        return False

    walls = []
    for i in range(h * 2 - 1):
        walls.append(list(map(int, input().split())))

    field = [[] for x in range(h * w)]

    for i in range(h):
        for j in range(w):
            f = j + i * w
            if j + 1 < len(walls[i]) and not walls[i*2][j]:
                    field[f].append(f + 1)
                    field[f + 1].append(f)
            if i + 1 < h and not walls[i*2 + 1][j]:
                field[f].append(f + w)
                field[f + w].append(f)
    # print(field)
    end = [False for x in range(w * h)]
    que = [(0, 0)]
    goal = h * w - 1
    results = []

    while que:
        tn, cost = que[0]
        del que[0]
        # print(tn)
        for n in field[tn]:
            if n == goal:
                results.append(cost)
                # print(end)
                # return True
            elif not end[n]:
                end[n] = True
                que.append((n, cost + 1))

    print(min(results) + 2 if results else 0)
    return True

while solve(): pass