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 INF 2147483647
#define lli long long int
#define MOD 1000000007
#define pb push_back

using namespace std;
typedef vector<int> vi;
typedef vector< vector<int> > vvi;
typedef pair<int,int> pii;
typedef vector<pair<int,int>> vpii;

bool C(vvi check, int nx, int ny){
	if (0 <= nx and nx < check.front().size() and 0 <= ny and ny < check.size()) {
		if (check[ny][nx] == 0) {
			return true;	
		}
	}
	return false;	
}

bool UB(vvi ub, int nx, int ny) {
	if (0 <= nx and nx < ub.front().size() and 0 <= ny and ny < ub.size()){
		if (ub[ny][nx] == 0) {
			return true;
		}	
	}
	return false;
}

bool LR(vvi lr, int nx, int ny) {
	if (0 <= nx and nx < lr.front().size() and 0 <= ny and ny < lr.size()){
		if (lr[ny][nx] == 0) {
			return true;
		}
	}
	return false;
}

int bfs(vvi ub, vvi lr) {

	int w = ub.front().size();
	int h = lr.size();
	vvi check(lr.size(),vi(ub.front().size(),0));
	check[0][0] = 1;
	queue<pii> q;
	q.push(make_pair(0,0));
	
	vi cx = {1,-1,0,0};	
	vi cy = {0,0,1,-1};	
	vi dx = {0,0,0,-1};	
	vi dy = {0,-1,0,0};	
	int ret = 0;
	while(!q.empty()) {
		pii now = q.front();
		//cout << "x = " << now.second << " y = " << now.first << endl;
		q.pop();
		if (now.first == ub.size() and now.second == lr.front().size()) {
			return check[now.first][now.second];
		}
		
		//right

		for (int i = 0; i < 4; i++) {
			int ccx = now.second + cx[i];	
			int ccy = now.first + cy[i];
			int ddx = now.second + dx[i];
			int ddy = now.first + dy[i];
			if (C(check,ccx,ccy) and UB(ub,ddx,ddy) and (i == 2 or i == 3)) {
				//cout << "UB" << endl;
				q.push(make_pair(ccy,ccx));
				check[ccy][ccx] += check[now.first][now.second] + 1;
			//	cout << ccx << " " << ccy << endl;
			}else if(C(check,ccx,ccy) and LR(lr,ddx,ddy) and  (i == 0 or i == 1)) {
				//cout << "LR" << endl;
				q.push(make_pair(ccy,ccx));
				check[ccy][ccx] += check[now.first][now.second] + 1;
			//	cout << ccx << " " << ccy << endl;
			}
			
			//cout << C(check,ccx,ccy) << " " << UB(ub,ddx,ddy) << " " <<  LR(lr,ddx,ddy) << endl;
		}

	}
	//cout << "empty" << endl;
	return 0;
}

int main() {
	while(1) {
		int w,h; cin >> w >> h;

		if (w + h == 0) break;

		vvi lr(h,vi(w-1,0));
		vvi ub(h-1,vi(w,0));

		for (int i = 0; i < h-1; i++) {
			for (int j = 0; j < w - 1; j++) {
				cin >> lr[i][j];	
			}
			for (int j = 0; j < w; j++) {
				cin >> ub[i][j];	
			}
		}
		for (int j = 0; j < w - 1; j++) {
				cin >> lr[h-1][j];	
		}

		cout << bfs(ub,lr) << endl;
	}
	return 0;
}

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

int block[61][61];
int dist[61][61];

const int di[] = {-1, 0, 1, 0};
const int dj[] = {0, -1, 0, 1};

int main() {
  while (1) {
    memset(dist, -1, sizeof(dist));
    int h, w;
    cin >> w >> h;
    if(w + h == 0) break;
    w = w * 2 - 1;
    h = h * 2 - 1;
    rep(i, h) {
      if (i % 2 == 0) {
        rep(j, w) if (j % 2 == 1) cin >> block[i][j];
      } else {
        rep(j, w) if (j % 2 == 0) cin >> block[i][j];
      }
    }

    queue<P> q;
    q.push(P(0, 0));
    dist[0][0] = 1;
    while (!q.empty()) {
      int i = q.front().first;
      int j = q.front().second;
      P now = P(i, j);
      q.pop();
      rep(d, 4) {
        int ni = i + di[d], nj = j + dj[d];
        if (ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
        if (block[ni][nj] == 1) continue;

        ni = i + di[d] * 2;
        nj = j + dj[d] * 2;
        if (dist[ni][nj] > 0) continue;
        dist[ni][nj] = dist[i][j] + 1;
        q.push(P(ni, nj));
      }
    }
    // rep(i, h) {
    //   rep(j, w) printf("%3d", dist[i][j]);
    //   cout << endl;
    // }
    int ans = max(0, dist[h - 1][w - 1]);
    cout << ans << endl;
  }
  return 0;
}