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 INF_LL (int64)1e18
#define INF (int32)1e9
#define REP(i, n) for(int64 i = 0;i < (n);i++)
#define FOR(i, a, b) for(int64 i = (a);i < (b);i++)
#define all(x) x.begin(),x.end()
#define fs first
#define sc second

using int32 = int_fast32_t;
using uint32 = uint_fast32_t;
using int64 = int_fast64_t;
using uint64 = uint_fast64_t;
using PII = pair<int32, int32>;
using PLL = pair<int64, int64>;

const double eps = 1e-10;

template<typename A, typename B>inline void chmin(A &a, B b){if(a > b) a = b;}
template<typename A, typename B>inline void chmax(A &a, B b){if(a < b) a = b;}

template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value!=0>::type
fill_v(U &u,const V... v){u=U(v...);}

template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value==0>::type
fill_v(U &u,const V... v){
  for(auto &e:u) fill_v<T>(e,v...);
}

int64 h, w;

int64 to_idx(int64 y, int64 x) {
  return y*w+x;
}

PLL to_pos(int64 idx) {
  return PLL(idx/h, idx%h);
}

int64 th = 0;
int main(void) {
  while ( cin >> w >> h && w + h) {
    auto G = make_v<PLL>(h*w, 0);
    REP(i, 2*h-1) {
      if (i % 2 == 0) {
        REP(j, w-1) {
          cin >> th;
          if (!th) {
            G[to_idx((i/2), j)].emplace_back(1, to_idx((i/2), j+1));
            G[to_idx((i/2), j+1)].emplace_back(1, to_idx((i/2), j));
          }
        }
      } else {
        REP(j, w) {
          cin >> th;
          if (!th) {
            G[to_idx(i/2, j)].emplace_back(1, to_idx(i/2+1, j));
            G[to_idx(i/2+1, j)].emplace_back(1, to_idx(i/2, j));
          }
        }
      }
    }
    priority_queue<PLL, vector<PLL>, greater<PLL>> pq;
    pq.emplace(0, 0);
    vector<int64> d(h*w, INF_LL);
    d[0] = 0;
    while (pq.size()) {
      int64 v, c;
      tie(c, v) = pq.top(); pq.pop();
      if (d[v] < c) continue;
      REP(i, G[v].size()) {
        int64 u, cc;
        tie(cc, u) = G[v][i];
        if (d[v] + cc < d[u]) {
          d[u] = d[v] + cc;
          pq.emplace(d[u], u);
        }
      }
    }
    if (d[to_idx(h-1, w-1)] == INF_LL) {
      cout << 0 << endl;
    } else {
      cout << d[to_idx(h-1, w-1)]+1 << endl;
    }
  }
}

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;
}