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
#include <cstdio>
#include <cmath>
#include <cstring>
#include <iostream>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <algorithm>
// }}}

using namespace std;

typedef long long ll;
inline int in(){int x;scanf("%d",&x);return x;}

int way[999][999];

const int INF = 1 << 28;

int main()
{
  int W, H;
  while (W = in(), H = in()){
    for (int i = 0; i < 999; i++){
      for (int j = 0; j < 999; j++){
        way[i][j] = INF;
      }
      way[i][i] = 0;
    }
    for (int x = 0; x < W - 1; x++){
      if (in() == 0) way[x][x + 1] = way[x + 1][x] = 1;
    }
    for (int y = 1; y < H; y++){
      for (int x = 0; x < W; x++){
        if (in() == 0) way[y * W + x][y * W + x - W] = way[y * W + x - W][y * W + x] = 1;
      }
      for (int x = 0; x < W - 1; x++){
        if (in() == 0) way[y * W + x][y * W + x + 1] = way[y * W + x + 1][y * W + x] = 1;
      }
    }
    for (int k = 0; k < W * H; k++){
      for (int i = 0; i < W * H; i++){
        for (int j = 0; j < W * H; j++){
          way[i][j] = min(way[i][j], way[i][k] + way[k][j]);
        }
      }
    }
    if (way[0][W * H - 1] == INF) cout << 0 << endl;
    else cout << way[0][W * H - 1] + 1 << endl;
  }
  return 0;
}

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

typedef pair<int, int> P;

int bfs[30][30];
int maze[100][100];

int main(){
	int w,h;
	while(scanf("%d%d",&w,&h) && w && h){
		for(int i = 0; i < 2*h-1 ;i++){
			for(int j = 0; j < w+i%2-1 ;j++){
				scanf("%d",&maze[i][j]);
			}
		}
		for(int i = 0; i < 30;i++)
			for(int j = 0; j < 30;j++)
				bfs[i][j] = 0;
		
        bfs[0][0] = 1;

		queue<P> q;
		q.push(P(0,0));

		while(q.size()){
			P p = q.front();
            int row = p.first;
            int col = p.second;
			q.pop();

			if(row){
				if(!maze[row*2-1][col] && !bfs[row-1][col]){
					bfs[row-1][col] = bfs[row][col]+1;
					q.push(P(row-1,col));
				}
			}
			if(row < h-1){
				if(!maze[row*2+1][col] && !bfs[row+1][col]){
					bfs[row+1][col] = bfs[row][col]+1;
					q.push(P(row+1,col));
				}
			}
			if(col){
				if(!maze[row*2][col-1] && !bfs[row][col-1]){
					bfs[row][col-1] = bfs[row][col]+1;
					q.push(P(row,col-1));
				}
			}
			if(col < w-1){
				if(!maze[row*2][col] && !bfs[row][col+1]){
					bfs[row][col+1] = bfs[row][col]+1;
					q.push(P(row,col+1));
				}
			}
		}
		printf("%d\n",bfs[h-1][w-1]);
	}
}

C++: // ACM-ICPCà\I2010 B. À}Æ½¸

#include <iostream>
#include <queue>

using namespace std;

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

int main(){
	int w, h;
	string s[59];
	int step[30][30];
	while(cin >> w >> h, w){
		getline(cin, s[0]);
		for(int i=0;i<2*h-1;i++) getline(cin, s[i]);
		for(int i=0;i<2*h-1;i++) s[i] += " ";
		memset(step, -1, sizeof(step));
		queue< pair<int, int> > qu; qu.push(make_pair(0,0));
		step[0][0] = 1;
		while(!qu.empty()){
			pair<int, int> p = qu.front(); qu.pop();
			int x = p.first, y = p.second;
			for(int i=0;i<4;i++){
				int nx = x+dx[i], ny = y+dy[i];
				if(nx<0||h<=nx||ny<0||w<=ny) continue;
				if(s[2*x+dx[i]][2*y+dy[i]]=='1') continue;
				if(step[nx][ny]!=-1) continue;
				step[nx][ny] = step[x][y] + 1;
				qu.push(make_pair(nx, ny));
			}
		}
		cout << (step[h-1][w-1] == -1 ? 0 : step[h-1][w-1]) << endl;
	}
}

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

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
int hs(int w, int h, P p){
	return w - p.first + h - p.second;
}
int main(){
	for(int w,h;;){
		cin>>w>>h;
		if(w+h==0)break;
		vector<vector<vector<P>>> g(w,vector<vector<P>>(h,vector<P>()));
		for(int d,i=1; i<=h; i++){
			for(int j=1; j<w; j++){
				cin>>d;
				if(!d){
					g[j-1][i-1].push_back(P(1,0));
					g[j][i-1].push_back(P(-1,0));
				}
			}
			if(i!=h){
				for(int j=0; j<w; j++){
					cin>>d;
					if(!d){
						g[j][i-1].push_back(P(0,1));
						g[j][i].push_back(P(0,-1));
					}
				}
			}
		}
		vector<vector<int>> d(w,vector<int>(h,INT_MAX));
		priority_queue<PP, vector<PP>, greater<PP>> q;
		q.push(PP(d[0][0]=1,P(0,0)));
		for(;q.size();){
			P now = q.top().second;
			int cost = d[now.first][now.second];
			q.pop();
			for(P v : g[now.first][now.second]){
				v.first += now.first;
				v.second += now.second;
				if(cost+1 < d[v.first][v.second]){
					q.push(PP(hs(h,w,v)+(d[v.first][v.second]=cost+1),v));
				}
			}
		}
		cout<<(d[w-1][h-1] < INT_MAX ? d[w-1][h-1] : 0)<<endl;
	}
}