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 <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-11;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

class Graph{
	private:
	int n;
	vvp g;
	public:
	int DIJ(int s,int t){
		priority_queue<P> q;
		vi d(n,inf);
		d[s]=0;
		q.push({0,s});
		while(!q.empty()){
			P p=q.top();
			q.pop();
			int v=p.second;
			if(d[v]<-p.first) continue;
			for(auto i:g[v]){
				int u=i.first,D=d[v]+i.second;
				if(d[u]>D){
					d[u]=D;
					q.push({-D,u});
				}
			}
		}
		return d[t];
	}
	Graph(int v){
		n=v;
		g=vvp(v);
	}
	void add_edge(int s,int t,int c){
		g[s].push_back({t,c});
		g[t].push_back({s,c});
	}
};

int main(){
	while(1){
		int h,w;
		cin>>w>>h;
		if(h==0) break;
		Graph g(h*w);
		for(int i=0;i<h;i++){
			for(int j=0;j<w-1;j++){
				int x;
				cin>>x;
				if(x==0) g.add_edge(i*w+j,i*w+j+1,1);
			}
			if(i<h-1){
				for(int j=0;j<w;j++){
					int x;
					cin>>x;
					if(x==0) g.add_edge(i*w+j,(i+1)*w+j,1);
				}
			}
		}
		int res=g.DIJ(0,h*w-1);
		if(res==inf) res=-1;
		cout<<res+1<<endl;
	}
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for(int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using pii = pair<int, int>;

int main() {
	int w, h;
	while (cin >> w >> h) {
		if (w == 0 && h == 0) break;
		vector<string> g(2 * h - 1);
		cin.ignore();
		rep(i, 2 * h - 1) {
			getline(cin, g[i]);
		}
		vector<vector<int>> d(h, vector<int>(w, -1));
		d[0][0] = 0;
		queue<pii> q;
		q.push({0, 0});
		while (!q.empty()) {
			pii p = q.front();
			q.pop();
			int y, x;
			tie(y, x) = p;
			vector<int> dy = {0, 1, 0, -1};
			vector<int> dx = {1, 0, -1, 0};
			rep(i, 4) {
				int ny = y + dy[i];
				int nx = x + dx[i];
				if (ny < 0 || ny >= h || nx < 0 || nx >= w) continue;
				//上下に進む -> g[2y+dy][2x]が0ならばok
				//左右に進む -> g[2y][2x+dx]が0ならばok
				if (g[ny + y][nx + x] == '1' || d[ny][nx] != -1) continue;
				d[ny][nx] = d[y][x] + 1;
				q.push({ny, nx});
			}
		}
		cout << d[h - 1][w - 1] + 1 << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <queue>
#include <utility>
#include <algorithm>
#define REP(i,n) for(int i=0;i<(n);i++)
using namespace std;

typedef pair<int, int> pxy;

typedef struct{
  bool u, d, l, r;
}Wall;

int w, h;
Wall map[50][50];
int d[50][50];

bool bfs(int sx, int sy)
{
  queue<pxy> q;
  q.push(pxy(sx, sy));
  while(!q.empty()){
    int x, y;
    x = q.front().first;
    y = q.front().second;
    q.pop();
    if(x == h - 1 && y == w - 1) return true;
    if(!map[x][y].u){
      d[x-1][y] = min(d[x-1][y], d[x][y] + 1);
      q.push(pxy(x-1,y));
    }
    if(!map[x][y].d){
      d[x+1][y] = min(d[x+1][y], d[x][y] + 1);
      q.push(pxy(x+1,y));
    }
    if(!map[x][y].l){
      d[x][y-1] = min(d[x][y-1], d[x][y] + 1);
      q.push(pxy(x,y-1));
    }
    if(!map[x][y].r){
      d[x][y+1] = min(d[x][y+1], d[x][y] + 1);
      q.push(pxy(x,y+1));
    }
    map[x][y].u = map[x][y].d = map[x][y].l = map[x][y].r = true;
    if(x >= 1)
      map[x-1][y].d = true;
    if(y >= 1)
      map[x][y-1].r = true;
    map[x+1][y].u = map[x][y+1].l = true;
  }
  return false;
}

int main()
{
  while(1){
    cin >> w >> h;
    if(w == 0 && h == 0) break;
    fill(&d[0][0], &d[50][0], 9999);
    d[0][0] = 1;
    REP(i,50){
      REP(j,50){
        map[i][j].u = map[i][j].d = map[i][j].l = map[i][j].r = false;
      }
    }
    REP(i,2*h-1){
      int x;
      if(i & 1){
        REP(j,w){
          cin >> x;
          if(x){
            map[i/2][j].d = map[i/2][j+1].u = true;
          }
        }
      }else{
        REP(j,w-1){
          cin >> x;
          if(x){
            map[i/2][j].r = map[i/2][j+1].l = true;
          }
        }
      }
    }
    REP(i,h)
      map[i][0].l = map[i][w-1].r = true;
    REP(i,w)
      map[0][i].u = map[h-1][i].d = true;
    if(bfs(0, 0))
      cout << d[h-1][w-1] << endl;
    else
      cout << "0" << endl;
  }
}