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 <string>
#include <map>
#include <vector>
#include <algorithm>
#include <queue>
#include <stack>
#include <cstdio>
#include <cmath>

using namespace std;

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define EPS 1e-14

#define all(v) v.begin(),v.end()
#define INF
#define mp make_pair
#define pb

#define fi first
#define se second


typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

typedef long long ll;
int s[30*2+10][30*2+10];
int dx[] = {-1,0,1,0};
int dy[] = {0,1,0,-1};
int main(){
	int t=0;
	while(1){
		//cout<<++t<<endl;
		rep(y,70){
			rep(x,70){
				s[y][x]=-1;
			}
		}
		int w,h;
		cin >> w >> h;
		//cout << w << " " << h << endl;
	
		if(w==0) break;
		rep(y,h*2+1){
			rep(x,w*2+1){
				if(y==0||x==0||y==h*2||x==w*2){
					s[y][x] = -1;
				}else if(x%2==0 && y%2==0){
					s[y][x] = -1;
				}else if((x+y)%2==0){
					s[y][x] = 0;
				}else{
					cin >> s[y][x];
					if(s[y][x]==1) s[y][x]=-1;
				}
			}
		}
		// rep(y,60){
		// 	rep(x,60){
		// 		printf("%c ",(s[y][x]==-1)? '#':' ');
		// 	}
		// 	cout << endl;
		// }
		// cout << endl;

		queue<pii> que;
		que.push(mp(1,1));
		while(!que.empty()){
			int x = que.front().fi;
			int y = que.front().se;
			//cout<<"@ "<<x<<" "<<y<<endl;
			//s[y][x] = dist.front();
			if(y == h*2-1 &&x == w*2-1){
				break;
			}
			int d = s[y][x];
			rep(i,4){
				int nx = x + dx[i];
				int ny = y + dy[i];
				if( nx>=0 && ny>=0 &&
					nx<w*2+1  && ny<h*2+1  &&
					s[ny][nx]==0){
					s[ny][nx] = d+1;
					que.push(mp(nx,ny));
				}
			}
			que.pop();
		}
		// rep(y,60){
		// 	rep(x,60){
		// 		printf("%2d ",s[y][x]);
		// 	}
		// 	cout << endl;
		// }
		//cout << endl;
		if(s[h*2-1][w*2-1]==0){
			cout << 0 << endl;
		}else{
			cout << s[h*2-1][w*2-1]/2+1 << endl;
		}
		//cout<<"fin"<<endl;
	}
	return 0;
}

C++: #include <cstdio>
#include <queue>
#include <algorithm>

#define N 30

using namespace std;

int
main (
  )
{
  int i, j;

  for ( ; ; )
  {
    typedef pair<int,int> P;
    queue<P> lis;
    int d[ N ][ N ] = { { 1 } };
    int v[ N ][ N ][ 4 ] = { };
    int w, h;
    int res = 0;
    int flg = 0;

    scanf ( "%d%d", &w, &h );
    if ( !( w | h ) ) break ;

    for ( i = 0; i < h; ++i )
    {
      if ( i > 0 )
      for ( j = 0; j < w; ++j )
      {
        int G__21;

        scanf ( "%d", &G__21 );
        v[ i ][ j - 1 ][ 1 ] =
        v[ i ][ j ][ 3 ] = G__21;
      }

      for ( j = 0; j < w - 1; ++j )
      {
        int G__21;

        scanf ( "%d", &G__21 );
        v[ i ][ j ][ 0 ] =
        v[ i ][ j + 1 ][ 2 ] = G__21;
      }
    }

    lis.push ( make_pair ( -1, -1 ) );
    lis.push ( make_pair ( 0, 0 ) );
    while ( !lis.empty ( ) )
    {
      P p = lis.front ( );
      lis.pop ( );

      if ( p.first == w - 1 && p.second == h - 1 )
      {
        printf ( "%d\n", res );
        break ;
      }
      if ( p.first < 0 && p.second < 0 )
      {
        if ( flg )
        {
          puts ( "0" );
          break ;
        }
        flg = 1;

        lis.push ( p );
        ++res;
        continue ;
      }
      flg = 0;

      if ( p.first < w - 1
        && !d[ p.second ][ p.first + 1 ]
        && !v[ p.second ][ p.first ][ 0 ] )
      {
        d[ p.second ][ p.first + 1 ] = 1;
        lis.push ( make_pair ( p.first + 1, p.second ) );
      }
      if ( p.second < h - 1
        && !d[ p.second + 1 ][ p.first ]
        && !v[ p.second ][ p.first ][ 1 ] )
      {
        d[ p.second + 1 ][ p.first ] = 1;
        lis.push ( make_pair ( p.first, p.second + 1 ) );
      }
      if ( p.first > 0
        && !d[ p.second ][ p.first - 1 ]
        && !v[ p.second ][ p.first ][ 2 ] )
      {
        d[ p.second ][ p.first - 1 ] = 1;
        lis.push ( make_pair ( p.first - 1, p.second ) );
      }
      if ( p.second > 0
        && !d[ p.second - 1 ][ p.first ]
        && !v[ p.second ][ p.first ][ 3 ] )
      {
        d[ p.second - 1 ][ p.first ] = 1;
        lis.push ( make_pair ( p.first, p.second - 1 ) );
      }
    }
  }

  return ( 0 );
}