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

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = mod * mod;
const int INF_N = 1e+9;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acos(-1.0);
//typedef vector<vector<ll>> mat;
typedef vector<int> vec;

//繰り返し二乗法
ll mod_pow(ll a, ll n, ll m) {
	ll res = 1;
	while (n) {
		if (n & 1)res = res * a%m;
		a = a * a%m; n >>= 1;
	}
	return res;
}

struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n%mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint &a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint &a, modint b) { a.n = ((ll)a.n*b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
	if (n == 0)return modint(1);
	modint res = (a*a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

//逆元(Eucledean algorithm)
ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1 << 18;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}
using mP = pair<modint, modint>;

int dx[4] = { 0,1,0,-1 };
int dy[4] = { 1,0,-1,0 };


struct Object {
    // 任意の構造体
    ll x;
    ll y;
    ll depth;
};

queue<Object> q;
int w, h;
vector<vec> v;
vector<vec> memo;
vector<vec> dist;

void bfs() {
    while (!q.empty()) {
        // キューの先頭の要素を取り出す dequeue(pop)
        Object now = q.front(); q.pop();
        
        // 停止条件
        // if (now.hoge == target) return ~;  // 探索対象
        // if (now.x == gx && now.y == gy) return now.depth;
        
        // BFS
        // west
        if(now.x != 0 && v[now.y*2][now.x-1] != 1 && dist[now.y][now.x-1] == -1){
            memo[now.y][now.x-1] = 1;
            dist[now.y][now.x-1] = now.depth+1;
            q.push({now.x-1, now.y ,now.depth+1});
        }
        // east
        if(now.x != w-1 && v[now.y*2][now.x] != 1 && dist[now.y][now.x+1] == -1){
            memo[now.y][now.x+1] = 1;
            dist[now.y][now.x+1] = now.depth+1;
            q.push({now.x+1, now.y, now.depth+1});
        }
        // north
        if(now.y != 0 && v[now.y*2-1][now.x] != 1 && dist[now.y-1][now.x] == -1){
            memo[now.y-1][now.x] = 1;
            dist[now.y-1][now.x] = now.depth+1;
            q.push({now.x, now.y-1, now.depth+1});
        }
        // south
        if(now.y != h-1 && v[now.y*2+1][now.x] != 1 && dist[now.y+1][now.x] == -1){
            memo[now.y+1][now.x] = 1;
            dist[now.y+1][now.x] = now.depth+1;
            q.push({now.x, now.y+1, now.depth+1});
        }

        // rep(i, 4){
        //     int nx = now.x + dx[i];
        //     int ny = now.y + dy[i];
        //     if(ny < 0 || ny >= 2*h-1 || nx < 0 || nx >= 2*w-1) continue;
        //     if(memo[ny][nx]) continue;
        //     if(v[ny][nx] == 1) continue;
        //     Object next = {nx, ny, now.depth+1};
        //     dist[ny][nx] = next.depth;
        //     memo[ny][nx] = 1;
        //     q.push(next);
        // }
    }
}

void solve() {
    while(cin >> w >> h, w+h){
        v = vector<vec>(2*h-1);
        memo = vector<vec>(h, vec(w, 0));
        dist = vector<vec>(h, vec(w, -1));
        rep(i, 2*h-1){
            rep(j, w-(i+1)%2){
                int a; cin >> a;
                v[i].push_back(a);
            }
        }

        memo[0][0] = 1;
        dist[0][0] = 1;
        q.push({0, 0, 1});
        bfs();
        
        if(dist[h-1][w-1] == -1){
            cout << 0 << endl;
        }else{
            cout << dist[h-1][w-1]<< endl;
        }
    }
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  //cout << fixed << setprecision(10);
  //init_f();
  //init();
  //int t; cin >> t; rep(i, t)solve();
  solve();
//   stop
    return 0;
}



Measured memory_bytes: 7264