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)
}

C++: #include<iostream>
#include<queue>

using namespace std;

#define MAX 50
#define INF 100000000

struct point{
	int x, y;
};

int main(){

	int w, h;
	int mize[MAX+2][MAX+2];
	int tw[MAX+2][MAX+2];
	int yw[MAX+2][MAX+2];
	point st, go, no, s;
	queue<point> qu;

		while (1){

		cin >> w >> h;
		if (w == 0 && h == 0) break;
		for (int i = 0; i <= MAX+1; i++){
			for (int j = 0; j <= MAX+1; j++){
				mize[i][j] = INF;
				tw[i][j] = 1;
				yw[i][j] = 1;
			}
		}
		for (int i = 1; i <= h; i++){
			for (int j = 1; j <= w - 1; j++){
				cin >> tw[i][j];
			}
			if (i != h){
				for (int j = 1; j <= w; j++){
					cin >> yw[i][j];
				}
			}
		}
		st.x = 1, st.y = 1;
		go.x = w, go.y = h;
		no.x = 1, no.y = 1;
		qu.push(no);
		mize[1][1] = 1;
		while (!qu.empty()){
			no = qu.front();
			qu.pop();
			if (tw[no.y][no.x] == 0 && mize[no.y][no.x] + 1 < mize[no.y][no.x + 1]){
				s.y = no.y, s.x = no.x + 1;
				mize[no.y][no.x + 1] = mize[no.y][no.x] + 1;
				qu.push(s);
			}
			if (tw[no.y][no.x + 1] == 0 && mize[no.y][no.x] + 1 < mize[no.y][no.x - 1]){
				s.y = no.y, s.x = no.x - 1;
				mize[no.y][no.x - 1] = mize[no.y][no.x] + 1;
				qu.push(s);
			}
			if (yw[no.y + 1][no.x] == 0 && mize[no.y][no.x] + 1 < mize[no.y - 1][no.x]){
				s.y = no.y - 1, s.x = no.x;
				mize[no.y - 1][no.x] = mize[no.y][no.x] + 1;
				qu.push(s);
			}
			if (yw[no.y][no.x] == 0 && mize[no.y][no.x] + 1 < mize[no.y + 1][no.x]){
				s.y = no.y + 1, s.x = no.x;
				mize[no.y + 1][no.x] = mize[no.y][no.x] + 1;
				qu.push(s);
			}
		}
		if (mize[go.y][go.x] == INF) cout << "0" << endl;
		else cout << mize[go.y][go.x] << endl;
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

#pragma GCC optimize "O3"
#define rep(i,a,n) for(long long i=a; i<n; i++)
typedef long long ll;
typedef pair<int,int> P;
const ll MOD = (int)1e9+7;
const ll INF = MOD*MOD;
const double EPS = 1e-9;
const ll powll = 1LL<<1;

/*
while(!frag && cin >> a >>b, a|b)
*/

int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};

int Maze[100][100];
int Wall[100][100][4];
int h, w;

int main(void){
    while(true)
    {

        cin >> w >> h;
        if(!(h || w)) break;

        // 初期化
        for(int i = 0; i < h; ++i) {
            for(int j = 0; j < w; ++j) {
                Maze[i][j] = -1;
                for(int k = 0; k < 4; ++k) {
                    Wall[i][j][k] = 0;
                }
            }
        }

        for(int i = 0; i < 2*h-1; ++i) {
            if(i%2== 0) {
                for(int j = 0; j < w-1; ++j) {
                    int k;
                    cin >> k;
                    // 縦でi/2番目のブロックの横の壁
                    Wall[i/2][j][1] = Wall[i/2][j+1][3] = k;
                }
            } else {
                for(int j = 0; j < w; ++j) {
                    int k;
                    cin >> k;
                    // 縦でi/2番目のブロックの下の壁
                    Wall[i/2][j][2] = Wall[i/2+1][j][0]= k;
                }
            }
        }

        queue<pair<int,int>> tsk;
        tsk.push(make_pair(0,0));
        //long long max_queue = 0;
        while(!tsk.empty())
        {
            //max_queue = max(max_queue, (long long)tsk.size());
            auto p = tsk.front();
            int x = p.first/w, y = p.first%w;
            tsk.pop();
            // ↓これを加えると、MLEを回避した。
            //if(Maze[x][y] != -1) continue;
            // ↑これを加えると、MLEを回避した。
            for(int i = 0; i < 4; ++i) {
                int nx = x + dx[i];
                int ny = y + dy[i];
                if(nx < 0 || nx >= h || ny < 0 || ny >= w) continue;
                if(Wall[x][y][i]) continue;
                if(Maze[nx][ny] != -1) continue;
                tsk.push(make_pair(nx*w + ny, p.second + 1));
                Maze[nx][ny] = p.second + 1;
            }
        }
        //cout << "max_queue: " << max_queue << endl;
        /*
        if(w == 2 && h == 3) {
            for(int i = 0; i < h; ++i) {
                for(int j = 0; j < w; ++j) {
                    cout << Maze[i][j] << " ";
                }
                cout << endl;
            }

        }
        */
        // ゴールは(h-1, w-1)
        cout << ((Maze[h-1][w-1] != -1) ? Maze[h-1][w-1] + 1 : 0 ) << endl;
    }
}