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 <iostream>
#include <queue>
using namespace std;

constexpr int INF = 1 << 30;

struct Info {
    int h;
    int w;
    int dist;
};

int main()
{
    while (true) {
        int w, h;
        cin >> w >> h;
        if (w == 0 and h == 0) {
            break;
        }
        vector<vector<bool>> yoko(h, vector<bool>(w - 1, true));  // (h,w)->(h,w+1)
        vector<vector<bool>> tate(h - 1, vector<bool>(w, true));  // (h,w)->(h+1, w)
        for (int i = 0; i < 2 * h - 1; i++) {
            if (i % 2 == 0) {
                for (int j = 0; j < w - 1; j++) {
                    int c;
                    cin >> c;
                    yoko[i / 2][j] = (c == 0);
                }
            } else {
                for (int j = 0; j < w; j++) {
                    int c;
                    cin >> c;
                    tate[i / 2][j] = (c == 0);
                }
            }
        }
        vector<vector<bool>> visited(h, vector<bool>(w, false));
        queue<Info> q;
        q.push(Info{0, 0, 1});
        int distance = INF;
        while (not q.empty()) {
            const Info p = q.front();
            q.pop();
            if (p.h == h - 1 and p.w == w - 1) {
                distance = p.dist;
                break;
            }
            if (p.dist > h * w) {
                break;
            }
            visited[p.h][p.w] = true;
            if (p.h != h - 1 and tate[p.h][p.w] and (not visited[p.h + 1][p.w])) {
                q.push(Info{p.h + 1, p.w, p.dist + 1});
            }
            if (p.h != 0 and tate[p.h - 1][p.w] and (not visited[p.h - 1][p.w])) {
                q.push(Info{p.h - 1, p.w, p.dist + 1});
            }
            if (p.w != w - 1 and yoko[p.h][p.w] and (not visited[p.h][p.w + 1])) {
                q.push(Info{p.h, p.w + 1, p.dist + 1});
            }
            if (p.w != 0 and yoko[p.h][p.w - 1] and (not visited[p.h][p.w - 1])) {
                q.push(Info{p.h, p.w - 1, p.dist + 1});
            }
        }

        if (distance != INF) {
            cout << distance << endl;
        } else {
            cout << 0 << endl;
        }
    }
    return 0;
}

C++: #include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <unordered_map>
#include <vector>

#define FOR(i,k,n) for (int (i)=(k); (i)<(n); ++(i))
#define rep(i,n) FOR(i,0,n)
#define pb push_back
#define all(v) begin(v), end(v)
#define debug(x) cerr<< #x <<": "<<x<<endl
#define debug2(x,y) cerr<< #x <<": "<< x <<", "<< #y <<": "<< y <<endl

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<i_i, int> p_i;
typedef vector<int> vi;
typedef vector<vector<int> > vvi;
template<class T> using vv=vector<vector<T> >;
typedef deque<int> di;
typedef deque<deque<int> > ddi;

int main() {
  vi results;

  while (true) {
    int w, h;
    cin >> w >> h;
    if (w==0) { break; }
    vvi vertical(h, vi(w+1, 1));
    vvi horizontal((h+1), vi(w, 1));
    
    for (int iw = 1; iw < w; iw++) {
      cin >> vertical[0][iw];
    }
    for (int ih = 1; ih < h; ih++) {
      for (int iw_hor = 0 ; iw_hor < w ; iw_hor++) {
        cin >> horizontal[ih][iw_hor];
      }
      for (int iw_ver = 1; iw_ver < w; iw_ver++) {
        cin >> vertical[ih][iw_ver];
      }
    }

    vvi md(h, vi(w, INT_MAX)); // min_distance, INT_MAX: not reached
    md[0][0] = 1;
    ddi bfs = {{0, 0}};
    while (!bfs.empty()) {
      di current = bfs.front(); // {h, w}
      vvi fq_ver = {{1, 1}, {0, -1}}; // wall, grid
      vvi fq_hor = {{1, 1}, {0, -1}}; // wall, grid
      for (auto dir : fq_ver) {
        if (vertical[current[0]][current[1] + dir[0]] == 0 &&
            md[current[0]][current[1] + dir[1]] == INT_MAX) {
          md[current[0]][current[1] + dir[1]] = md[current[0]][current[1]] + 1;
          bfs.push_back({current[0], current[1] + dir[1]});
        }
      }
      for (auto dir : fq_hor) {
        if (horizontal[current[0] + dir[0]][current[1]] == 0 &&
            md[current[0] + dir[1]][current[1]] == INT_MAX) {
          md[current[0] + dir[1]][current[1]] = md[current[0]][current[1]] + 1;
          bfs.push_back({current[0] + dir[1], current[1]});
        }
      }
      bfs.pop_front();
    }
    if (md[h-1][w-1] == INT_MAX) {
      md[h-1][w-1] = 0;
    }
    results.push_back(md[h-1][w-1]);
  }

  for (int i = 0 ; i < results.size() ; i++) {
    printf("%d\n", results[i]);
  }

  return 0;
}