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 heapq

    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, end)]
    goal = h * w - 1
    results = []

    while que:
        tn, cost, end = que[0]
        del que[0]
        for n in field[tn]:
            if n == goal:
                results.append(cost)
                print(cost + 2)
                return True
            elif not end[n]:
                end[n] = True
                que.append((n, cost + 1, end[:]))

    print(0)
    return True

while solve(): pass

Python: from collections import deque
while True:
    W,H = map(int, input().split())
    if W == 0: break
    es = [[] for i in range(W*H)]
    for y in range(H):
        walls_h = map(int, input().split())
        for x in range(W-1):
            if walls_h[x]: continue
            es[y*W + x].append(y*W + x+1)
            es[y*W + x+1].append(y*W + x)
        if y == H-1: break
        walls_v = map(int, input().split())
        for x in range(W):
            if walls_v[x]: continue
            es[y*W + x].append((y+1)*W + x)
            es[(y+1)*W + x].append(y*W + x)
    q = deque()
    q.append(0)
    dist = [0] * (W*H)
    dist[0] = 1
    while q:
        fr = q.popleft()
        for to in es[fr]:
            if dist[to] == 0:
                dist[to] = dist[fr] + 1
                q.append(to)
    print(dist[-1])

Python: from copy import deepcopy
while True:
    w, h = map(int, input().split())
    if w == 0:
        break
    wwal = []  # ｜
    hwal = []  # ー
    a = [0] * w
    b = []
    for i in range(2 * h - 1):
        if i % 2 == 0:
            wwal.append(list(map(int, input().split())))
            c = deepcopy(a)
            b.append(c)
        else:
            hwal.append(list(map(int, input().split())))
    b[0][0] = 1
    start = [[0, 0]]
    flag = 0
    while flag == 0:
        flag = 1
        stamemo = []
        for i in range(len(start)):
            t = start.pop()
            # Left
            if t[1] != 0:
                if wwal[t[0]][t[1] - 1] == 0 and b[t[0]][t[1]-1] == 0:
                    b[t[0]][t[1] - 1] = b[t[0]][t[1]] + 1
                    stamemo.append([t[0], t[1] - 1])
                    flag = 0
            # righT
            if t[1] != w-1:
                if wwal[t[0]][t[1]] == 0 and b[t[0]][t[1]+1] == 0:
                    b[t[0]][t[1] + 1] = b[t[0]][t[1]] + 1
                    if t[0] == h - 1 and t[1] + 1 == w - 1:
                        print(b[t[0]][t[1] + 1])
                        flag = 2
                        break
                    stamemo.append([t[0], t[1]+1])
                    flag = 0
            # Up
            if t[0] != 0:
                if hwal[t[0] - 1][t[1]] == 0 and b[t[0] - 1][t[1]] == 0:
                    b[t[0] - 1][t[1]] = b[t[0]][t[1]] + 1
                    stamemo.append([t[0] - 1, t[1]])
                    flag = 0
            # dowN
            if t[0] != h-1:
                if hwal[t[0]][t[1]] == 0 and b[t[0] + 1][t[1]] == 0:
                    b[t[0] + 1][t[1]] = b[t[0]][t[1]] + 1
                    if t[0]+1 == h - 1 and t[1] == w - 1:
                        print(b[t[0]+1][t[1]])
                        flag = 2
                        break
                    stamemo.append([t[0] + 1, t[1]])
                    flag = 0
        start = stamemo
        print(start)
    if flag == 1:
        print(0)