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: while(True):
  A, B = map(int, input().split())
  if (A == 0 and B ==0):
    break
  vert = []
  hori = []

  hist = {}

  for i in range(B - 1):
    vert.append(list(map(int, input().split())))
    hori.append(list(map(int, input().split())))

  vert.append(list(map(int, input().split())))

  next_pos = [{"x": 0, "y": 0, "step": 0}]
  hist['0::0'] = 0
  while(True):
    if (len(next_pos) == 0):
      pos = {}
      pos["step"] = 0
      break
    pos = next_pos.pop(0)
    
    if (pos["x"] == A - 1 and pos["y"] == B - 1):
      pos["step"] += 1
      break

    # 右方向への移動
    if (f'{pos["x"] + 1}::{pos["y"]}' not in hist and pos["x"] < A - 1 and pos["y"] < B and vert[pos["y"]][pos["x"]] == 0):
      next_pos.append({"x": pos["x"] + 1, "y": pos["y"], "step": pos["step"] + 1})
      hist[f'{pos["x"] + 1}::{pos["y"]}'] = 0

    # 下方向への移動
    if (f'{pos["x"]}::{pos["y"] + 1}' not in hist and pos["x"] < A and pos["y"] < B - 1 and hori[pos["y"]][pos["x"]] == 0):
      next_pos.append({"x": pos["x"], "y": pos["y"] + 1, "step": pos["step"] + 1})
      hist[f'{pos["x"]}::{pos["y"] + 1}'] = 0

    # 左方向への移動
    if (f'{pos["x"] - 1}::{pos["y"]}' not in hist and pos["x"] - 1 >= 0 and pos["y"] < B and vert[pos["y"]][pos["x"] - 1] == 0):
      next_pos.append({"x": pos["x"] - 1, "y": pos["y"], "step": pos["step"] + 1})
      hist[f'{pos["x"] - 1}::{pos["y"]}'] = 0

    # 上方向への移動
    if (f'{pos["x"]}::{pos["y"] - 1}' not in hist and pos["x"] < A and pos["y"] - 1 >= 0 and hori[pos["y"] - 1][pos["x"]] == 0):
      next_pos.append({"x": pos["x"], "y": pos["y"] - 1, "step": pos["step"] + 1})
      hist[f'{pos["x"]}::{pos["y"] - 1}'] = 0

  print(pos["step"])

Python: from queue import Queue

while True:
    w, h = map(int, input().split())
    if w == h == 0:
        break

    vl = list()
    hl = list()
    for i in range(h * 2 - 1):
        if i % 2:
            hl.append(list(map(int, input().split())))
        else:
            vl.append(list(map(int, input().split())))

    q = Queue()
    d = [[w * h + 1 for i in range(h)] for j in range(w)]
    q.put((0, 0))
    d[0][0] = 1
    while not q.empty():
        x, y = q.get()

        if x > 0 and (not vl[y][x - 1]) and d[x - 1][y] > h * w:
            d[x - 1][y] = d[x][y] + 1
            q.put((x - 1, y))

        if x < w - 1 and (not vl[y][x]) and d[x + 1][y] > h * w:
            d[x + 1][y] = d[x][y] + 1
            q.put((x + 1, y))

        if y > 0 and (not hl[y - 1][x]) and d[x][y - 1] > h * w:
            d[x][y - 1] = d[x][y] + 1
            q.put((x, y - 1))

        if y < h - 1 and (not hl[y][x]) and d[x][y + 1] > h * w:
            d[x][y + 1] = d[x][y] + 1
            q.put((x, y + 1))
    
    if d[w - 1][h - 1] > h * w:
        print(0)
    else:
        print(d[w - 1][h - 1])

Python: from collections import deque
from sys import stdin
input = stdin.readline

while True:
    W,H = map(int, input().split())
    if W == 0 and H == 0:
        break
    
    wallcolumn = [None]*H
    wallrow = [[1]*W] + [None]*(H-1) + [[1]*W]
    for h in range(H):
        wallcolumn[h] = [1] + list(map(int, input().split())) + [1]
        if h < H-1:
            wallrow[h+1] = list(map(int, input().split()))
    
    distancemat = [[-1]*W for _ in range(H)]#-1のとき未探索
    queue = deque()
    queue.append((0,0))
    distancemat[0][0] = 1
    
    while queue:
        x,y = queue.popleft()
        distance = distancemat[y][x]
        #左方向
        if x > 0:
            if wallcolumn[y][x] == 0 and distancemat[y][x-1] == -1:
                distancemat[y][x-1] = distance + 1
                queue.append((x-1,y))
        #右方向
        if x < W-1:
            if wallcolumn[y][x+1] == 0 and distancemat[y][x+1] == -1:
                distancemat[y][x+1] = distance + 1
                queue.append((x+1,y))
        #上方向
        if y > 0:
            if wallrow[y][x] == 0 and distancemat[y-1][x] == -1:
                queue.append((x,y-1))
                distancemat[y-1][x] = distance + 1
        #下方向
        if y < H-1:
            if wallrow[y+1][x] == 0 and distancemat[y+1][x] == -1:
                queue.append((x,y+1))
                distancemat[y+1][x] = distance + 1
    
    if distancemat[H-1][W-1] == -1:
        print(0)
    else:
        print(distancemat[H-1][W-1])