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 <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>

using namespace std;

#define f first
#define s second

typedef pair<int, int> P;
typedef pair<int, P> P2;

int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};

int W, H;
bool yoko[31][31];
bool tate[31][31];

int bfs(){
  int cnt = 1;
  set<P> check;
  queue<P2> que;
  que.push(P2(cnt, P(0, 0)));
  
  while(!que.empty()){
    P2 t = que.front();
    que.pop();
    if(check.find(P(t.s.f, t.s.s)) == check.end()){
      check.insert(P(t.s.f, t.s.s));
      if(t.s.f == W-1 && t.s.s == H-1) return t.f;
      for(int i = 0 ; i < 4 ; i++){
	P2 tmp = t;
	tmp.s.f += dx[i];
	tmp.s.s += dy[i];
	tmp.f++;
	if(tmp.s.f < 0 || tmp.s.f >= W || tmp.s.s < 0 || tmp.s.s >= H) continue;
	if(dx[i] == 1 && tate[t.s.s][t.s.f]) continue;
	if(dx[i] == -1 && tate[tmp.s.s][tmp.s.f]) continue;
	if(dy[i] == 1 && yoko[t.s.s][t.s.f]) continue;
	if(dy[i] == -1 && yoko[tmp.s.s][tmp.s.f]) continue;
	que.push(tmp);
      }
    }
  }
  return 0;
}


int main(){
  while(cin >> W >> H){
    if(W == 0 && H == 0) break;
    memset(tate, 0, sizeof(tate));
    memset(yoko, 0, sizeof(yoko));
    
    for(int i = 0 ; i < 2*H-1 ; i++){
      if(i % 2 == 0){
	for(int j = 0 ; j < W-1 ; j++){
	  cin >> tate[i/2][j];
	}
      }
      else{
	for(int j = 0 ; j < W ; j++){
	  cin >> yoko[i/2][j];
	}
      }
    }
    
    cout << bfs() << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
vector<int> dy = {1, 0, -1, 0};
vector<int> dx = {0, 1, 0, -1};
int INF = 10000;
int main(){
  while (1){
    int w, h;
    cin >> w >> h;
    if (w == 0 && h == 0){
      break;
    }
    vector<vector<vector<bool>>> ok(h, vector<vector<bool>>(w, vector<bool>(4, true)));
    for (int i = 0; i < w; i++){
      ok[h - 1][i][0] = false;
      ok[0][i][2] = false;
    }
    for (int i = 0; i < h; i++){
      ok[i][w - 1][1] = false;
      ok[i][0][3] = false;
    }
    for (int i = 0; i < h * 2 - 1; i++){
      if (i % 2 == 0){
        for (int j = 0; j < w - 1; j++){
          int x;
          cin >> x;
          if (x == 1){
            ok[i / 2][j][1] = false;
            ok[i / 2][j + 1][3] = false;
          }
        }
      }
      if (i % 2 == 1){
        for (int j = 0; j < w; j++){
          int x;
          cin >> x;
          if (x == 1){
            ok[i / 2][j][0] = false;
            ok[i / 2 + 1][j][2] = false;
          }
        }
      }
    }
    vector<vector<int>> d(h, vector<int>(w, INF));
    d[0][0] = 1;
    queue<pair<int, int>> Q;
    Q.push(make_pair(0, 0));
    while (!Q.empty()){
      int y = Q.front().first;
      int x = Q.front().second;
      Q.pop();
      for (int i = 0; i < 4; i++){
        if (ok[y][x][i]){
          int y2 = y + dy[i];
          int x2 = x + dx[i];
          if (d[y2][x2] == INF){
            d[y2][x2] = d[y][x] + 1;
            Q.push(make_pair(y2, x2));
          }
        }
      }
    }
    if (d[h - 1][w - 1] == INF){
      cout << 0 << endl;
    } else {
      cout << d[h - 1][w - 1] << endl;
    }
  }
}

C++: #include <bits/stdc++.h>
using namespace std;

constexpr int inf = 0x3f3f3f3f;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int w, h;
  while (cin >> w >> h, w) {
    auto $ = [&](int i, int j) {
      return i * w + j;
    };
    vector<set<int>> g(h * w);
    for (int i = 0; i < h; ++i) {
      for (int j = 0; j < w; ++j) {
        if (i + 1 < h) {
          g[$(i, j)].insert($(i + 1, j));
          g[$(i + 1, j)].insert($(i, j));
        }
        if (j + 1 < w) {
          g[$(i, j)].insert($(i, j + 1));
          g[$(i, j + 1)].insert($(i, j));
        }
      }
    }
    for (int i = 0; i < 2 * h - 1; ++i) {
      if (i % 2 == 0) {
        for (int j = 0; j < w - 1; ++j) {
          int x;
          cin >> x;
          if (x) {
            g[$(i / 2, j)].erase($(i / 2, j + 1));
            g[$(i / 2, j + 1)].erase($(i / 2, j));
          }
        }
      } else {
        for (int j = 0; j < w; ++j) {
          int x;
          cin >> x;
          if (x) {
            g[$(i / 2, j)].erase($(i / 2 + 1, j));
            g[$(i / 2 + 1, j)].erase($(i / 2, j));
          }
        }
      }
    }
    vector<int> d(h * w, inf);
    queue<int> que;
    d[$(0, 0)] = 0;
    que.push($(0, 0));
    while (not que.empty()) {
      int v = que.front();
      que.pop();
      for (int u : g[v]) {
        if (d[u] == inf) {
          d[u] = d[v] + 1;
          que.push(u);
        }
      }
    }
    int res = d[$(h - 1, w - 1)];
    cout << (res < inf ? res + 1 : 0) << '\n';
  }
}