#define _CRT_SECURE_NO_WARNINGS
#pragma warning(disable: 4244) // 最悪をします
#include <iostream>
#include <cmath>
#include <algorithm>
#include <vector>
#include <numeric>
#include <queue>
#include <stack>
#include <map> 
#include <set>
#include <string>
#include <functional>
#include <list>
#include <random>
#include <time.h>
#include <iomanip>
#include <assert.h>
#include <numeric>
#include <sstream>
#define BIT(nr) (1UL << (nr))
#define int long long
//#define ll long long
#define double long double
#define mod 1000000007
#define MAXN (int)1e+5 * 2+1
#define LL_MAX 9223372036854775807	//ない環境用
#define LL_HALFMAX 9223372036854775807 / 2	//ない環境用
#define MIN -(9223372036854775807 / 2)
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
#define REPS(i,x) for(int i=1;i<=(int)(x);i++)
#define RREP(i,x) for(int i=((int)(x)-1);i>=0;i--)
#define RREPS(i,x) for(int i=((int)(x));i>0;i--)
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define mp make_pair
template<typename T1, typename T2> inline void chmin(T1 & a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }


using namespace std;

//デバッグ用カッコの有無
#ifdef DEBUG
template <class T>ostream &operator<<(ostream &o, const vector<T>&v)
{
	o << "{"; for (int i = 0; i<(int)v.size(); i++)o << (i>0 ? ", " : "") << v[i]; o << "}"; return o;
}
#endif // DEBUG

template <class T>ostream &operator<<(ostream &o, const vector<T>&v)
{
	for (int i = 0; i<(int)v.size(); i++)o << (i>0 ? " " : "") << v[i]; return o;
}

int dx[4] = { 0, 1, 0, -1 }; // x軸方向への変位
int dy[4] = { 1, 0, -1, 0 }; // y軸方向への変位

int dxp[4] = { 0, 1 }; // x軸方向への変位(正のみ)
int dyp[4] = { 1, 0 }; // y軸方向への変位(負のみ)

using Weight = int;
using Flow = int;
struct Edge {
	int src, dst;

	// libalgo のものに追加、メンバを追加するだけなので互換性は崩さないはず、逆辺のG[e.dstの]インデックスを保持
	int rev;
	Weight weight;
	Flow cap;
	Edge() : src(0), dst(0), weight(0) {}
	Edge(int s, int d, Weight w) : src(s), dst(d), weight(w) {}
};
using Edges = std::vector<Edge>;
using Graph = std::vector<Edges>;
using Array = std::vector<Weight>;
using Matrix = std::vector<Array>;

void add_edge(Graph& g, int a, int b, Weight w = 1) {
	g[a].emplace_back(a, b, w);
	g[b].emplace_back(b, a, w);
}
void add_arc(Graph& g, int a, int b, Weight w = 1) { g[a].emplace_back(a, b, w); }

bool solve() {
	int w, h;
	cin >> w >> h;

	if (w == 0 && h == 0) {
		return false;
	}

	vector<vector<int>> wallY(h, vector<int>(w - 1, 0));
	vector<vector<int>> wallX(h - 1, vector<int>(w, 0));

	rep(i, 2 * h - 1) {
		if (i % 2 == 0) {
			rep(j, w - 1) {
				cin >> wallY[i / 2][j];
			}
		}
		else {
			rep(j, w) {
				cin >> wallX[i / 2][j];
			}
		}
	}

	queue<pair<int, int>> q;
	vector<vector<int>> dist(h, vector<int>(w, -1));
	vector<vector<bool>> visited(h, vector<bool>(w, false));

	q.emplace(0, 0);
	dist[0][0] = 0;

	while (!q.empty()) {
		auto p = q.front();
		q.pop();
		int x = p.first, y = p.second;

		if (visited[y][x]) {
			continue;
		}
		visited[y][x] = true;

		rep(i, 4) {
			int nx = x + dx[i], ny = y + dy[i];
			if (nx < 0 || ny < 0 || nx >= w || ny >= h) {
				continue;
			}
			if (visited[ny][nx]) {
				continue;
			}

			// x 方向の移動
			if (dy[i] == 0) {
				if (dx[i] == 1 && wallY[y][x] == 1) {
					continue;
				}
				if (dx[i] == -1 && wallY[y][x - 1] == 1) {
					continue;
				}
			}
			// y 方向の移動
			else {
				if (dy[i] == 1 && wallX[y][x] == 1) {
					continue;
				}
				if (dy[i] == -1 && wallX[y - 1][x] == 1) {
					continue;
				}
			}

			dist[ny][nx] = dist[y][x] + 1;
			q.emplace(nx, ny);
		}
	}

	if (dist[h - 1][w - 1] == -1) {
		cout << 0 << "\n";
	}
	else {
		cout << dist[h - 1][w - 1] + 1 << "\n";
	}
	return true;
}

signed main() {
	while (solve()) {}
}



Measured memory_bytes: 3184