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 <stdio.h>
#include <utility>
#include <queue>
#include <string.h>

using namespace std;
int main(void)
{
    while(true) {
        queue< pair<int,int> > q;
        int w,h,map[1000][1000],visited[900],res=-1;

        scanf("%d%d", &w, &h);
        if(!w && !h) break;

        memset( map, 0, sizeof(map) );
        memset( visited, 0, sizeof(map) );

        for(int i=0; i < h-1; i++) {
            for(int j=0; j < w-1; j++) {
                int in;
                scanf("%d", &in);
                if(!in) {
                    map[i*w+j][i*w+j+1] = 1;
                    map[i*w+j+1][i*w+j] = 1;
                }
            }
            for(int j=0; j < w; j++) {
                int in;
                scanf("%d", &in);
                if(!in) {
                    map[i*w+j][(i+1)*w+j] = 1;
                    map[(i+1)*w+j][i*w+j] = 1;
                }
            }
        }
        {
            int i=h-1;
            for(int j=0; j < w-1; j++) {
                int in;
                scanf("%d", &in);
                if(!in) {
                    map[i*w+j][i*w+j+1] = 1;
                    map[i*w+j+1][i*w+j] = 1;
                }
            }
        }

        q.push(make_pair(0,0));
        while(!q.empty() && res==-1) {
            int p,d;
            std::pair<int,int> t;

            t=q.front(); q.pop();
            p=t.first;
            d=t.second;
//            printf(":%d:",map[p][p+h]);

            visited[p] = 1;

            if(p==w*h-1) {
                res = d;
            }

            if(map[p][p+1] && !visited[p+1])
                q.push(make_pair(p+1, d+1));

            if(map[p][p-1] && !visited[p-1])
                q.push(make_pair(p-1, d+1));

            if(map[p][p+w] && !visited[p+w])
                q.push(make_pair(p+w, d+1));

            if(p-w >= 0 && map[p][p-w] && !visited[p-w])
                q.push(make_pair(p-w, d+1));

        }
        printf("%d\n", res+1);
    }
    return 0;
}

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


class Graph {
  public:
    int n_node;
    vector<vector<int>> edge;

    Graph(int n_node) : n_node(n_node){
      edge.resize(n_node);
    };

    void add_edge(int i, int j);
};

void Graph::add_edge(int i, int j) {
  // cout << i << ", " << j << endl;
  edge[i].push_back(j);
}

int main() {
  int w, h, c;
  int block;


  while (cin >> w >> h, w) {
    Graph g(w*h);

    rep (i, 2*h-1) {
      if (i%2 == 0) {
        // yoko
        rep (j, w-1) {
          cin >> block;
          int offset = w * (i / 2);
          int c = offset + j;
          if (block == 0) g.add_edge(c, c+1);
          if (block == 0) g.add_edge(c+1, c);
        }
      }
      else {
        // tate
        rep (j, w) {
          int offset = w * ((i - 1) / 2);
          cin >> block;
          c = j + offset;
          if (block == 0) g.add_edge(c, c+w);
          if (block == 0) g.add_edge(c+w, c);
        }
      }
    }

    // bfs
    queue<int> que;
    que.push(0);

    vector<int> cost(w*h);
    rep (i, w*h) cost[i] = 1001001001;
    cost[0] = 1;

    while (!que.empty()) {
      int current = que.front(); que.pop();

      for (int next_ : g.edge[current]) {
        if (cost[next_] == 1001001001) {
          que.push(next_);
          cost[next_] = cost[current] + 1;
          // cout << "current: " << current << ", next: " << next_ << endl;
          // cout << "current_cost: " << cost[current] << endl;
        }
      }
    }

    if (cost[w*h-1] == 1001001001) {
      cout << 0 << endl;
    }
    else {
      cout << cost[w*h-1] << endl;
    }
  }
  return 0;
}