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 <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <queue>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <complex>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <stdio.h>

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<double> VEC;
typedef vector<VEC> MAT;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<int, PII> TIII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
//container util

//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define MT(a,b,c) MP(a, MP(b, c))
#define T1 first
#define T2 second.first
#define T3 second.second

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define EPS 1.0e-9

vector<PII> tt[30][30];
int dist[30][30];

int main(){
	int w,h;
	while(cin>>w>>h,w){
		REP(i,30)REP(j,30)tt[i][j].clear();
		memset(dist, -1, sizeof(dist));
		REP(i,2*h-1){
			int tmp;
			if(i%2==0){
				REP(j,w-1){
					cin>>tmp;
					if(tmp==0){
						tt[i/2][j].PB(MP(i/2, j+1));
						tt[i/2][j+1].PB(MP(i/2, j));
					}
				}
			}else{
				REP(j,w){
					cin>>tmp;
					if(tmp==0){
						tt[i/2][j].PB(MP(i/2+1, j));
						tt[i/2+1][j].PB(MP(i/2, j));
					}
				}
			}
		}
		priority_queue<TIII, vector<TIII>, greater<TIII> > q;
		q.push(MT(0, 0, 0));
		int flag = 0;
		while(!q.empty()){
			TIII tmp = q.top();
			q.pop();
			if(dist[tmp.T2][tmp.T3]!=-1)continue;
			dist[tmp.T2][tmp.T3]=tmp.T1;
			if(tmp.T2==h-1 && tmp.T3==w-1){
				cout << tmp.T1+1 << endl;
				flag = 1;
				break;
			}
			REP(i, tt[tmp.T2][tmp.T3].size())q.push(MT(tmp.T1+1, tt[tmp.T2][tmp.T3][i].first, tt[tmp.T2][tmp.T3][i].second));
		}
		if(!flag)cout << 0 << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <map>
#include <queue>
using namespace std;

typedef pair<int,int> P;
const int MAX_W = 30*2+1;
const int MAX_H = MAX_W;
int W, H;
bool G[MAX_H][MAX_W];

void init() {
  fill(G[0], G[MAX_H], 0);
  for(int i = 1; i < H; i += 2) {
    for(int j = 1; j < W; j += 2) {
      G[i][j] = 1;
    }
  }
}

int solve() {
  const static int dx[] = {1,0,-1,0};
  const static int dy[] = {0,1,0,-1};
  queue<P> que;
  int vis[MAX_H][MAX_W];
  fill(vis[0], vis[MAX_H], -1);
  vis[0][0] = 2;
  que.push(P(0,0));
  while(!que.empty()) {
    P p = que.front();
    que.pop();
    for(int k = 0; k < 4; ++k) {
      int nx = p.first + dx[k];
      int ny = p.second + dy[k];
      if(nx < 0 || nx >= W) continue;
      if(ny < 0 || ny >= H) continue;
      if(vis[ny][nx] != -1) continue;
      if(G[ny][nx]) continue;
      vis[ny][nx] = vis[p.second][p.first] + 1;
      if(nx == W-1 && ny == H-1) return vis[ny][nx]/2;
      que.push(P(nx,ny));
    }
  }
  return 0;
}

int main() {
  while(cin >> W >> H && (W | H)) {
    W = W*2-1;
    H = H*2-1;
    init();
    for(int i = 0; i < H; ++i) {
      for(int j = 1-i%2; j < W; j += 2) {
	cin >> G[i][j];
      }
    }
    cout << solve() << endl;
  }
  return 0;
}