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 enld '\n'
#define rep(i,n) for(int i=0; i<(n); i++)
using namespace std;
using ll = long long;
using P = pair<int,int>;
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("Ofast")
constexpr ll INF = 1e18;
constexpr int inf = 1e9;
constexpr double INFD = 1e100;
constexpr ll mod = 1000000007;
constexpr ll mod2 = 998244353;
const double PI = 3.1415926535897932384626433832795028841971;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
// ios::sync_with_stdio(false);
// cin.tie(nullptr);
// ---------------------------------------------------------------------------

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int H,W;
    cin >> W >> H;
    while(H != 0){
        vector<vector<int>> G(H*W);
        for(int i=0; i<H*2-1; i++){
            for(int j=0; j<(i%2 ? W : W-1); j++){
                int a;
                cin >> a;
                if(!a){
                    int h = i/2;
                    if(i%2 == 0){
                        G[h*W+j].push_back(h*W+j+1);
                        G[h*W+j+1].push_back(h*W+j);
                    }else{
                        G[(h+1)*W+j].push_back(h*W+j);
                        G[h*W+j].push_back((h+1)*W+j);
                    }
                }
            }
        }
        vector<int> dist(H*W,-1);
        dist[0] = 1;
        queue<int> que;
        que.push(0);
        while(que.size()){
            int v = que.front();
            que.pop();
            for(int nv: G[v]){
                if(dist[nv] != -1) continue;
                dist[nv] = dist[v] + 1;
                que.push(nv);
            }
        }
        // for(int i=0; i<H; i++){
        //     for(int j=0; j<W; j++){
        //         cout << dist[i*H+j] << " ";
        //     }
        //     cout << enld;
        // }
        // for(int i=0; i<W*H; i++){
        //     cout << i << " check: ";
        //     for(int j=0; j<G[i].size(); j++){
        //         cout << G[i][j] << " ";
        //     }
        //     cout << enld;
        // }
        if(dist[H*W-1] != -1){
            cout << dist[H*W-1] << enld;
        }else{
            cout << 0 << enld;
        }
        cin >> W >> H;
    }
    return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
#define val(i,j) ((i)*n+(j))
#define INF (1<<20)
int dist[108000];
int n, m, x;
vector<int> edge[108000];
bool solve(){
	cin >> n >> m;
	if(n == 0 && m == 0)return false;
	for(int i = 0;i < m;i++)
		for(int j = 0;j < n;j++){
			dist[val(i,j)] = INF;
			edge[val(i,j)].clear();
		}

	for(int i = 0;i < m-1;i++){
		for(int j = 0;j < n-1;j++){
			cin >> x;
			if(x==1)continue;
			edge[val(i,j)].push_back(val(i,j+1));
			edge[val(i,j+1)].push_back(val(i,j));
		}
		for(int j = 0;j < n;j++){
			cin >> x;
			
			if(x==1)continue;
			edge[val(i,j)].push_back(val(i+1,j));
			edge[val(i+1,j)].push_back(val(i,j));
		}
	}
	for(int j = 0;j < n-1;j++){
		cin >> x;
		if(x==1)continue;
		edge[val(m-1,j)].push_back(val(m-1,j+1));
		edge[val(m-1,j+1)].push_back(val(m-1,j));
	}

	queue<int> q;
	
	q.push(val(0,0));
	dist[val(0,0)] = 0;
	
	while(!q.empty()){
		int now = q.front();q.pop();
		for(int i = 0;i < edge[now].size();i++){
			int to = edge[now][i];
			if(dist[to] != INF)continue;
			dist[to] = dist[now] + 1;
			q.push(to);
		}
	}
	if(dist[val(m-1,n-1)] == INF)dist[val(m-1,n-1)] = -1;
	cout << dist[val(m-1,n-1)]+1 << endl;
	return true;
}

int main(){
	while(solve());
	return 0;
}