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 <cstdio>
#include <algorithm>

#define rep(i,n) for(int i=0;i<(n);i++)

using namespace std;

const int INF=1<<29;
const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};

int main(){
	for(int h,w;scanf("%d%d",&w,&h),h;){
		int hor[50][50],ver[50][50];
		rep(i,h){
			rep(j,w-1) scanf("%d",ver[i]+j);
			if(i<h-1){
				rep(j,w) scanf("%d",hor[i]+j);
			}
		}

		int d[50][50];
		rep(i,h) rep(j,w) d[i][j]=INF;
		d[0][0]=1;
		rep(_,h*w){
			rep(i,h) rep(j,w) rep(k,4) {
				int y=i+dy[k],x=j+dx[k];
				if(k==0 && ver[ i ][ j ]==0
				|| k==1 && hor[i-1][ j ]==0
				|| k==2 && ver[ i ][j-1]==0
				|| k==3 && hor[ i ][ j ]==0) d[y][x]=min(d[y][x],d[i][j]+1);
			}
		}
		printf("%d\n",d[h-1][w-1]<INF?d[h-1][w-1]:0);
	}

	return 0;
}

C++: #include<iostream>
#include<stack>
#include<utility>
#define INF 10000000
using namespace std;
int fw[30][30],fh[30][30];
bool used[30][30];
int w,h;
int d[30][30];
int cnt;
void dfs(){
  stack<pair<pair<int,int>,int> > sta;
  sta.push(make_pair(make_pair(0,0),1));
  while(!sta.empty()){
    pair<pair<int,int> ,int> q=sta.top(); sta.pop();
    int x=q.first.first,y=q.first.second;
    int cnt=q.second;
    if(d[x][y]<=cnt) continue;
    d[x][y]=cnt;
    cnt++;
    if(x!=0&&fh[x-1][y]==0) sta.push(make_pair(make_pair(x-1,y),cnt));
    if(y!=0&&fw[x][y-1]==0) sta.push(make_pair(make_pair(x,y-1),cnt));
    if(x!=h-1&&fh[x][y]==0) sta.push(make_pair(make_pair(x+1,y),cnt));
    if(y!=w-1&&fw[x][y]==0) sta.push(make_pair(make_pair(x,y+1),cnt));
  }
}
int main(){
  cin >> w >> h;
  while(w!=0){
    cnt=0;
    for(int i=0;i<2*h-1;i++){
      if(i%2==0){
        for(int j=0;j<w-1;j++){
          cin >> fw[i/2][j];
        }
      }else{
        for(int j=0;j<w;j++){
          cin >> fh[i/2][j];
        }
      }
    }
    for(int i=0;i<30;i++){
      for(int j=0;j<30;j++){
        used[i][j]=false;
        d[i][j]=INF;
      }
    }
    dfs();
    if(d[h-1][w-1]==INF) d[h-1][w-1]=0;
    cout << d[h-1][w-1]<<endl;
    cin >> w >> h;
  }
}

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

struct P
{
	int x,y;
};

P getP(int x,int y){
	P p={x,y};
	return p;
}

int main(){
	int w,h;
	int dx[]={0,0,-1,1};
	int dy[]={-1,1,0,0};

	while(cin >> w >> h, w|h){

		vector< vector<bool> > map;
		vector<bool>b;

		for(int ix=0;ix<w*2-1+2;ix++)
			b.push_back(true);
		map.push_back(b);

		for(int iy=0;iy<h*2-1;iy++){
			b.clear();
			b.push_back(true);
			if(iy%2==0){
				for(int ix=0;ix<w*2-1;ix++){
					bool t=0;
					if(ix%2==1)
						cin >> t;
					b.push_back(t);
				}
			}else{
				for(int ix=0;ix<w*2-1;ix++){
					bool t=0;
					if(ix%2==0)
						cin >> t;
					b.push_back(t);
				}
			}
			b.push_back(true);
			map.push_back(b);
		}
		b.clear();
		for(int ix=0;ix<w*2-1+2;ix++)
			b.push_back(true);
		map.push_back(b);

		queue<P> que;
		que.push(getP(1,1));
		que.push(getP(0,0));
		int path=0;
		while(!que.empty()){

			P p=que.front();que.pop();
			if(p.x==0&&p.y==0){
				path++;
				if(que.empty()){
					path=-1;
					break;
				}
				que.push(getP(0,0));
				continue;
			}
			if(p.x==w*2-1&&p.y==h*2-1)
				break;

			/*
			cout << endl;
			for(int iy=0;iy<map.size();iy++){
				for(int ix=0;ix<map.at(iy).size();ix++)
				if(p.x!=ix||p.y!=iy)
					cout << map[iy][ix];
				else
					cout << X;
				cout << endl;
			}
			cout << endl;
			*/

			if(!(p.x+p.y))path++;
			map[p.y][p.x]==true;
			for(int i=0;i<4;i++){
				if(!map[p.y+dy[i]][p.x+dx[i]]){
					map[p.y+dy[i]][p.x+dx[i]]=true;
					que.push(getP(p.x+dx[i]*2,p.y+dy[i]*2));
				}
			}
		}
		cout << path+1 << endl;
	}

	return 0;
}