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 explore(curlis,visited):
    global can
    if can==1 or curlis==[]:
        return
    i,j,k = curlis.pop(0)
    visited[i][j]=True
    if i == h-1 and j == w-1:
        print(k)
        visited.append("G")
        can=1
    for x,y in move:
        if check(i,j,x,y):
            visited[i+x][j+y]=True
            curlis.append([i+x,j+y,k+1])
    explore(curlis,visited)
		
		
def check(i,j,x,y):
    if 0<=i+x<h and 0<=j+y<w:
        if not visited[i+x][j+y]:
            if x==1:
                if orimap[2*i+1][j]:
                    return False
            if x==-1:
                if orimap[2*i-1][j]:
                    return False
            if y==1:
                if orimap[2*i][j]:
                    return False
            if y==-1:
                if orimap[2*i][j-1]:
                    return False
            return True
    return False

import sys
sys.setrecursionlimit(10000000)
move = ((0,1),(1,0),(-1,0),(0,-1))
w,h = map(int,input().split())
while w!=0 and h!=0:
    can=0
    orimap = []
    visited = []
    for _ in range((h*2)-1):
        if _ % 2==0:
            orimap.append(list(map(int,input().split()))+[1])
            visited.append([False]*w)
        elif _ % 2==1:
            orimap.append(list(map(int,input().split())))
    orimap.append([1]*w)
    explore([[0,0,1]],visited)
    if not can:
        print(0)
    w,h=map(int,input().split())

Python: #! cat testin | python3 main.py
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)]
    goal = h * w - 1
    results = []

    while que:
        tn, cost = 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))

    print(0)
    return True

while solve(): pass

Python: import sys
import math
from collections import defaultdict, deque
from copy import deepcopy
    
input = sys.stdin.readline
def RD(): return input().rstrip()
def F(): return float(input().rstrip())
def I(): return int(input().rstrip())
def MI(): return map(int, input().split())
def MF(): return map(float,input().split())
def LI(): return list(map(int, input().split()))
def LF(): return list(map(float,input().split()))
def Init(H, W, num): return [[num for i in range(W)] for j in range(H)]
    
    
def main():
    move = [[1,0],[0,1],[-1,0],[0,-1]]
    while True:
        W, H = MI()
        result = 0
        if W == 0 and H == 0:
            sys.exit()
        maze = [LI() for i in range(2*H-1)]
        goal = [H-1,W-1]
        d = Init(H,W,-1)
        dq = deque()
        dq.append([0,0])
        d[0][0] = 0
        while dq:
            ht, wt = dq.popleft()
            for h, w in move:
                h += ht
                w += wt
                if h >= 0 and w >= 0 and h < H and w < W and d[h][w] == -1:
                    if ht != h:
                        if maze[2*min(ht, h)+1][w] == 0:
                            dq.append([h,w])
                            d[h][w] = d[ht][wt]+1
                            if h == goal[0] and w == goal[1]:
                                result = d[h][w]+1
                                break
                    elif wt != w:
                        #横への移動が可能か
                        if maze[2*h][min(w, wt)] == 0:
                            dq.append([h,w])
                            d[h][w] = d[ht][wt]+1
                            if h == goal[0] and w == goal[1]:
                                result = d[h][w]+1
                                break
            else:
                continue
            break
        print(result)

    
if __name__ == "__main__":
    main()