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;
#define int long long   // <-----!!!!!!!!!!!!!!!!!!!

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
#define rrep2(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define all(a) (a).begin(),(a).end()

typedef long long ll;
typedef pair<int, int> P;
typedef tuple<int, int, int> TUPLE;
typedef vector<int> V;
typedef vector<V> VV;
typedef vector<VV> VVV;

const int INF = 1e9;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int H, W;
int s[50][50][2];   // 0:x(down), 1:y(right)

bool inside(int x, int y) {
    return 0 <= x && x < H && 0 <= y && y < W;
}

int bfs(int sx = 0, int sy = 0, int gx = H - 1, int gy = W - 1) {
    queue<P> que;
    que.push(P(sx, sy));
    vector<vector<int>> d(H, vector<int>(W, INF));
    d[sx][sy] = 1;

    while (!que.empty()) {
        int x, y;
        tie(x, y) = que.front(); que.pop();
        if (x == gx && y == gy)
             break;

        rep(k, 4) {
            int nx = x + dx[k], ny = y + dy[k];

            if (inside(nx, ny) && !s[min(x, nx)][min(y, ny)][x == nx] && d[nx][ny] == INF) {
                que.push(P(nx, ny));
                d[nx][ny] = d[x][y] + 1;
            }
        }
    }

    return (d[gx][gy] == INF ? 0 : d[gx][gy]);
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    while (cin >> W >> H, W) {
        rep(i, 2 * H - 1) {
            if (i % 2 == 0) {
                rep(j, W - 1) {
                    cin >> s[i / 2][j][1];
                }
            }
            else {
                rep(j, W) {
                    cin >> s[i / 2][j][0];
                }
            }
        }

        cout << bfs() << endl;
    }
}

C++: #include "bits/stdc++.h"
 
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef pair<int,int> pii;
#define int ll
#define fi first
#define se second
#define SORT(a) sort(a.begin(),a.end())
#define rep(i,n) for(int i = 0;i < (n) ; i++) 
#define REP(i,n) for(int i = 0;i < (n) ; i++) 
#define MP(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define INF LLONG_MAX/2
#define all(x) (x).begin(),(x).end()
#define debug(x) cerr<<#x<<": "<<x<<endl
#define debug_vec(v) cerr<<#v<<":";rep(i,v.size())cerr<<" "<<v[i];cerr<<endl
/*----------------------------------------------------------------*/

// int MOD = 998244353;
int MOD = 1000000007;

int h,w;
vector<int> G[910];

#define MAX_V 910
int V = 909;
int d[MAX_V];
void dijkstra(int s){
    priority_queue<pii,vector<pii>,greater<pii>> que;
    fill(d,d+V,INF);
    d[s] = 0;
    que.push(pii(0,s));
    while(!que.empty()){
        pii p = que.top();
        que.pop();
        int v = p.se;
        if(d[v] < p.fi) continue;
        for(auto x:G[v]){
            if(d[x] > d[v]+1){
                d[x] = d[v] + 1;
                que.push(pii(d[x],x));
            }
        }
    }
}

/*----------------------------------------------------------------*/
signed main(){

    while(1){
        cin >> w >> h;
        if(w == 0 && h == 0)break;
        rep(i,910)G[i].clear();
        int in;
        rep(i,h-1){
            rep(j,w-1){
                cin >> in;
                // cerr << in;
                if(in == 0){
                    G[i*w+j].pb(i*w+j+1);
                    G[i*w+j+1].pb(i*w+j);
                }
            }
            // cerr << endl;
            rep(j,w){
                cin >> in;
                // cerr << in;
                if(in == 0){
                    G[i*w+j].pb((i+1)*w+j);
                    G[(i+1)*w+j].pb(i*w+j);
                }
            }
            // cerr << endl;
        }
        rep(j,w-1){
            cin >> in;
            // cerr << in;
            if(in == 0){
                G[(h-1)*w+j].pb((h-1)*w+j+1);
                G[(h-1)*w+j+1].pb((h-1)*w+j);
            }
        }
        // cerr << endl;
        dijkstra(0);
        if(d[h*w-1] == INF)cout << 0 << endl;
        else cout << d[h*w-1]+1 << endl;
        // rep(i,h){
        //     rep(j,w){
        //         cerr << d[i*w+j] << " ";
        //     }cerr << endl;
        // }
    }   
    
	return 0;
}
/*----------------------------------------------------------------*/

// g++ -std=c++14 code1.cpp
// sudo pip3 install --upgrade online-judge-tools
// rm -r -f test;oj dl https://code-festival-2018-quala.contest.atcoder.jp/tasks/code_festival_2018_quala_c
// rm -r -f test;oj dl https://pakencamp-2019-day3.contest.atcoder.jp/tasks/pakencamp_2019_day3_c
// rm -r -f test;oj dl https:/joi2012yo.contest.atcoder.jp/tasks/joi2012yo_e