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>
using namespace std;
using Grid = vector<vector<int>>;

int	calc_dist(int w, int h, const vector<vector<int>>& w_wall,
		const vector<vector<int>> &h_wall)
{
	Grid	dist(h, vector<int>(w, -1));
	queue<pair<int, int>>	que;
	int	dx[4] = {1, 0, -1, 0};
	int	dy[4] = {0, 1, 0, -1};
	int sx = 0, sy = 0, gx = w - 1, gy = h - 1;
	int cx, cy, nx, ny;
	que.push(make_pair(sy, sx));
	dist.at(sy).at(sx) = 1;
	while (!que.empty() && dist.at(gy).at(gx) == -1) {
		cy = que.front().first;
		cx = que.front().second;
		que.pop();
		for (int i = 0; i < 4; ++i) {
			ny = cy + dy[i];
			nx = cx + dx[i];
			if (ny < 0 || h <= ny || nx < 0 || w <= nx)
				continue;
			if (i % 2 == 0 && w_wall.at(cy).at(min(nx, cx)))
				continue;
			if (i % 2 == 1 && h_wall.at(min(cy, ny)).at(cx))
				continue;
			if (dist.at(ny).at(nx) != -1)
				continue;
			dist.at(ny).at(nx) = dist.at(cy).at(cx) + 1;
			que.push(make_pair(ny, nx));
		}
	}
	return max(0, dist.at(gy).at(gx));
}

int	main()
{
	int	w, h;
	while (cin >> w >> h) {
		if (w == 0 && h == 0)
			break;
		vector<vector<int>>	w_wall(h, vector<int>(w - 1));
		vector<vector<int>>	h_wall(h - 1, vector<int>(w));
		for (int i = 0; i < 2 * h - 1; ++i) {
			if (i % 2 == 0) {
				for (int j = 0; j < w - 1; ++j)
					cin >> w_wall.at(i / 2).at(j);
			} else {
				for (int j = 0; j < w; ++j)
					cin >> h_wall.at(i / 2).at(j);
			}
		}
		cout << calc_dist(w, h, w_wall, h_wall) << endl;
	}
}

C++: #include <iostream>
#include <cstdio>
#include <cassert>
#include <cstring>
#include <vector>
#include <valarray>
#include <array>
#include <queue>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <cmath>
#include <complex>
#include <random>

using namespace std;
using ll = long long;
using ull = unsigned long long;
constexpr int TEN(int n) {return (n==0)?1:10*TEN(n-1);}

const int d4[4][2] = {
    {1, 0},
    {0, 1},
    {-1, 0},
    {0, -1},
};

bool solve() {
    int w, h;
    cin >> w >> h;
    if (!w or !h) return false;
    w = 2*w-1; h = 2*h-1;
    bool g[h][w];
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            g[i][j] = false;
        }
    }
    for (int i = 0; i < h; i++) {
        for (int j = 1-i%2; j < w; j += 2) {
            int k;
            cin >> k;
            g[i][j] = k == 1;
        }
    }
    using P = pair<int, int>;
    queue<P> q;
    bool used[h][w];
    int dist[h][w];
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            used[i][j] = false;
            dist[i][j] = 1<<28;
        }
    }
    q.push(P(0, 0));
    dist[0][0] = 1;
    while (q.size()) {
        P p = q.front(); q.pop();
        int x, y;
        tie(x, y) = p;
        if (used[y][x]) continue;
        used[y][x] = true;
//        printf("%d %d %d\n", x, y,dist[y][x]);
        for (int d = 0; d < 4; d++) {
            int nx = x+2*d4[d][0], ny = y+2*d4[d][1];
            if (!(0 <= nx and nx < w and 0 <= ny and ny < h)) continue;
            if (g[(y+ny)/2][(x+nx)/2]) continue;
            dist[ny][nx] = min(dist[ny][nx], dist[y][x]+1);
            q.push(P(nx, ny));
        }
    }
    if (dist[h-1][w-1] == 1<<28) dist[h-1][w-1] = 0;
    printf("%d\n", dist[h-1][w-1]);
    return true;
}

int main() {
    while (true) {
        if (!solve()) break;
    }
    return 0;
}