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 rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = 1001001001;
const int MOD = 1000000007;

template <typename T>
void print(const T &v);

int main()
{
    while (1)
    {
        int h, w;
        cin >> w >> h;
        if (w == 0 && h == 0)
        {
            return 0;
        }
        int grid[h][w][4]; // 1が通行可能
        vector<vector<int>> score(h, vector<int>(w, INF));
        for (int i = 0; i < (2 * h) - 1; i++)
        {
            if (i % 2 == 0)
            {
                for (int j = 0; j < w - 1; j++)
                {
                    int num;
                    cin >> num;
                    if (num == 0)
                    {
                        grid[i / 2][j][1] = 1;
                        grid[i / 2][j + 1][3] = 1;
                    }
                    else
                    {
                        grid[i / 2][j][1] = 0;
                        grid[i / 2][j + 1][3] = 0;
                    }
                }
            }
            else
            {
                for (int j = 0; j < w; j++)
                {
                    int num;
                    cin >> num;
                    if (num == 0)
                    {
                        grid[i / 2][j][2] = 1;
                        grid[(i / 2) + 1][j][0] = 1;
                    }
                    else
                    {
                        grid[i / 2][j][2] = 0;
                        grid[(i / 2) + 1][j][0] = 0;
                    }
                }
            }
        }

        queue<P> qe;
        qe.push(make_pair(0, 0));
        score[0][0] = 0;
        while (!qe.empty())
        {
            P now = qe.front();
            qe.pop();
            int x = now.first;
            int y = now.second;
            int xs[4] = {0, 1, 0, -1};
            int ys[4] = {-1, 0, 1, 0};
            for (int i = 0; i < 4; i++)
            {
                // 進む権利があるかを確認

                if (grid[y][x][i] == 0)
                {
                    continue;
                }
                int nx = x + xs[i];
                int ny = y + ys[i];
                if (nx < 0 || ny < 0 || ny >= h || nx >= w)
                {
                    continue;
                }
                if (score[ny][nx] <= score[y][x] + 1)
                {
                    continue;
                }
                if (score[ny][nx] != INF)
                {
                    score[ny][nx] = score[y][x] + 1;
                    continue;
                }
                score[ny][nx] = score[y][x] + 1;
                qe.push(make_pair(nx, ny));
            }
        }
        int goal = score[h - 1][w - 1];
        if (goal != INF)
        {
            cout << score[h - 1][w - 1] + 1 << endl;
        }
        else
        {
            cout << 0 << endl;
        }
    }
    return 0;
}

// Use For Debug
template <typename T>
void print(T const &v)
{
    for (int i = 0; i < v.size(); i++)
    {
        if (i)
            cout << ' ';
        cout << v[i];
    }
    cout << endl;
}

C++: #include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(i64 (i) = (s);(i) < (e);(i)++)
#define all(x) x.begin(),x.end()
#define let auto const

int main() {
  i64 w, h;
  while(cin >> w >> h, w && h) {
    vector<vector<i64>> fie(2 * h + 1, vector<i64>(2 * w + 1, -1));
    rep(i,0,h) rep(j,0,w) fie[i * 2 + 1][j * 2 + 1] = 0;

    rep(i, 1, 2 * h) {
      if(i & 1) {
        rep(j, 1, w) {
          i64 a;
          cin >> a;
          if(a == 1) fie[i][j * 2] = -1;
          else fie[i][j * 2] = 1;
        }
      }
      else {
        rep(j,0,w) {
          i64 a;
          cin >> a;
          if(a == 1) fie[i][j * 2 + 1] = -1;
          else fie[i][j * 2 + 1] = 1;
        }
      }
    }

    vector<vector<i64>> dist(2 * h + 1, vector<i64>(2 * w + 1, 1e18));
    using P = pair<i64, i64>;
    queue<P> que;
    que.push({1, 1});
    dist[1][1] = 0;

    vector<i64> d = {0, 1, 0, -1};
    
    while(!que.empty()) {
      i64 x = que.front().first;
      i64 y = que.front().second;
      que.pop();
      rep(q, 0, 4) {
        i64 xx = x + d[q];
        i64 yy = y + d[q ^ 1];
        if(fie[xx][yy] == -1) continue;
        if(dist[xx][yy] > dist[x][y] + fie[xx][yy]) {
          dist[xx][yy] = dist[x][y] + fie[xx][yy];
          que.push(P(xx, yy));
        }
      }
    }
    if(dist[h * 2 - 1][w * 2 - 1] == 1e18) { dist[h * 2 - 1][w * 2 - 1] = -1; }
    cout << dist[h * 2 - 1][w * 2 - 1] + 1 << endl;
  }
}