#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <limits>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define eprintf(...) 42
#endif
using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vvvll = std::vector<vvll>;
#define reps(i, S, E) for (ll i = (S); i <= (E); i++)
#define rep(i, N) reps(i, 0, N-1)
#define deps(i, E, S) for (ll i = (E); i >= (S); i--)
#define dep(i, N) deps(i, N-1, 0)
const ll INF = 1LL << 60;
const int INF_INT = 1 << 30;

template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
struct mll {
	static ll MOD;
	ll val;
	mll(ll v = 0) : val(v % MOD) { if (val < 0) val += MOD; }
	mll operator - () const { return -val; }
	mll operator + (const mll &b) const { return val + b.val; }
	mll operator - (const mll &b) const { return val - b.val; }
	mll operator * (const mll &b) const { return val * b.val; }
	mll operator / (const mll &b) const { return mll(*this) /= b; }
	mll operator + (ll b) const { return *this + mll(b); }
	mll operator - (ll b) const { return *this - mll(b); }
	mll operator * (ll b) const { return *this * mll(b); }
	friend mll operator + (ll a, const mll &b) { return b + a; }
	friend mll operator - (ll a, const mll &b) { return -b + a; }
	friend mll operator * (ll a, const mll &b) { return b * a; }
	mll &operator += (const mll &b) { val = (val + b.val) % MOD; return *this; }
	mll &operator -= (const mll &b) { val = (val + MOD - b.val) % MOD; return *this; }
	mll &operator *= (const mll &b) { val = (val*b.val) % MOD; return *this; }
	mll &operator /= (const mll &b) {
		ll c = b.val, d = MOD, u = 1, v = 0;
		while (d) {
			ll t = c / d;
			c -= t * d; swap(c, d);
			u -= t * v; swap(u, v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll &operator += (ll b) { return *this += mll(b); }
	mll &operator -= (ll b) { return *this -= mll(b); }
	mll &operator *= (ll b) { return *this *= mll(b); }
	mll &operator /= (ll b) { return *this /= mll(b); }
	bool operator == (const mll &b) { return val == b.val; }
	bool operator != (const mll &b) { return val != b.val; }
	bool operator == (ll b) { return *this == mll(b); }
	bool operator != (ll b) { return *this != mll(b); }
	friend bool operator == (ll a, const mll &b) { return mll(a) == b.val; }
	friend bool operator != (ll a, const mll &b) { return mll(a) != b.val; }
	friend ostream &operator << (ostream &os, const mll &a) { return os << a.val; }
	friend istream &operator >> (istream &is, mll &a) { return is >> a.val; }
	static mll Combination(ll a, ll b) {
		chmin(b, a - b);
		if (b < 0) return mll(0);
		mll c = 1;
		rep(i, b) c *= a - i;
		rep(i, b) c /= i + 1;
		return c;
	}
};
using vmll = std::vector<mll>;
using vvmll = std::vector<vmll>;
using vvvmll = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;

struct Fast {
	Fast() {
		cin.tie(0);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(std::numeric_limits<double>::max_digits10);
	}
} fast; //cin,cout高速化のおまじない＋桁数指定

ll mll::MOD = (ll)(1e9 + 7);// 998244353ll;


int main() {
	while (true) {
		ll W;
		cin >> W;
		ll H;
		cin >> H;

		if (W == 0 && H == 0) {
			break;
		}

		vvll maze(H * 2, vll(W * 2, 0));
		for (int i = 1; i < H * 2; i += 2) {
			for (int j = 1; j < W * 2; j += 2) {
				maze[i][j] = 1;
			}
		}
		rep(i, 2 * H - 1) {
			if (i % 2 == 0) {
				rep(j, W - 1) {
					ll M;
					cin >> M;
					if (M > 0) {
						maze[i][j * 2 + 1] = 1;
					}
				}
			}
			else {
				rep(j, W) {
					ll M;
					cin >> M;
					if (M > 0) {
						maze[i][j * 2] = 1;
					}
				}
			}
		}

		eprintf("\n");
		rep(i, H * 2) {
			rep(j, W * 2) {
				eprintf("%c", maze[i][j] == 0 ? '.' : '#');
			}
			eprintf("\n");
		}
		eprintf("\n");

		vvll d(H * 2, vll(W * 2, -1));
		queue<pair<ll, ll>> q;

		d[0][0] = 0;
		q.emplace(0, 0);
		while (q.empty() == false) {
			auto curr = q.front();
			q.pop();

			reps(i, -1, 1) reps(j, -1, 1) {
				//4近傍以外の場合
				if ((i == 0 && j == 0) || (abs(i) + abs(j) > 1)) {
					continue;
				}

				//範囲外
				if (curr.first + i < 0 || curr.second + j < 0 || curr.first + i >= H * 2 || curr.second + j >= W * 2) {
					continue;
				}

				//通れない場所
				if (maze[curr.first + i][curr.second + j] == 1) {
					continue;
				}

				//既に探索済み
				if (d[curr.first + i][curr.second + j] >= 0) {
					continue;
				}

				//キューに入れて探索継続
				d[curr.first + i][curr.second + j] = d[curr.first][curr.second] + 1;
				q.emplace(curr.first + i, curr.second + j);
			}
		}

		ll result = d[H * 2 - 1][W * 2 - 2] == -1 ? 0 : d[H * 2 - 1][W * 2 - 2] / 2 + 1;
		cout << result << endl;
	}

	return 0;
}



Measured memory_bytes: 3208