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>
#include <cstring>
using namespace std;

class State{
public:
  int x, y, cost;
  State(int _x, int _y, int _cost){
    x = _x;
    y = _y;
    cost = _cost;
  }
};

int w, h;
int t[100][100];
bool closed[100][100];

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

void solve(){
  queue<State> open;
  memset(closed, 0, sizeof(closed));
  open.push(State(0, 0, 0));

  while(!open.empty()){
    State st = open.front(); open.pop();
    if(closed[st.y][st.x]) continue;
    closed[st.y][st.x] = true;

    if(st.y == h - 1 && st.x == w - 1){
      cout << st.cost / 2 + 1 << endl;
      return;
    }

    for(int i = 0; i < 4; i++){
      int nx = st.x + dx[i];
      int ny = st.y + dy[i];

      if(0 <= nx && nx < w && 0 <= ny && ny < h && t[ny][nx] == 0){
        open.push(State(nx, ny, st.cost + 1));
      }
    }
  }

  cout << 0 << endl;
}

int main(){
  while(cin >> w >> h, w || h){
    w = w * 2 - 1;
    h = h * 2 - 1;

    for(int i = 0; i < h; i++){
      for(int j = 0; j < w; j++){
        if(i % 2 == 0){
          if(j % 2 == 0){
            t[i][j] = 0;
          }
          else{
            int x;
            cin >> x;
            t[i][j] = x;
          }
        }
        else{
          if(j % 2 == 0){
            int x;
            cin >> x;
            t[i][j] = x;
          }
          else{
            t[i][j] = 1;
          }
        }
      }
    }

    /*
    for(int i = 0; i < h; i++){
      for(int j = 0; j <w; j++){
        cout<<t[i][j];
      }
      cout<<endl;
    }
    */

    solve();
  }
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <climits>
#include <queue>
using namespace std;

#define INF INT_MAX/3
#define MP make_pair

typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

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

void solve(int H,int W){
    int maze[41][41];
    for(int i=0;i<2*H-1;i++){
        if(i%2==0){
            for(int j=0;j<W-1;j++) cin>>maze[i][j];
        }else{
            for(int j=0;j<W;j++) cin>>maze[i][j];
        }
    }

    //(0,0) -> (H-1,W-1)
    vector<vector<int>> d(H,vector<int>(W,INF));
    d[0][0] = 1;
    queue<pii> que;
    que.push(MP(0,0));
    while(!que.empty()){
        pii q = que.front();
        que.pop();
        int x = q.first;
        int y = q.second;
        
        for(int i=0;i<4;i++){
            int nx = x + dx[i];
            int ny = y + dy[i];
            if(nx<0 or ny<0 or nx>=H or ny>=W) continue;
            if(i==0 and maze[2*x+1][y]==0 and d[nx][ny]==INF){
                d[nx][ny]=d[x][y]+1;
                que.push(MP(nx,ny));
            }
            if(i==1 and maze[2*x][y]==0 and d[nx][ny]==INF){
                d[nx][ny]=d[x][y]+1;
                que.push(MP(nx,ny));
            }
            if(i==2 and maze[2*x-1][y]==0 and d[nx][ny]==INF){
                d[nx][ny]=d[x][y]+1;
                que.push(MP(nx,ny));
            }
            if(i==3 and maze[2*x][y-1]==0 and d[nx][ny]==INF){
                d[nx][ny]=d[x][y]+1;
                que.push(MP(nx,ny));
            }
        }
    }

    if(d[H-1][W-1]==INF){
        cout << 0 << endl;
        return;
    }
    cout << d[H-1][W-1] << endl;
    return;
}

int main(){
    int w,h;
    while(cin>>w>>h){
        if(w==0 and h==0) break;
        solve(h,w);
    }
}