#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <vector>
#include <string>
#include <queue>
#include <deque>
#include <list>
#include <stack>
#include <set>
#include <map>
#include <algorithm>

#define int long long
#define MOD7 1000000007
#define MOD9 1000000009

#define rep(i, n) for (int i = 0; i < (n); i++)
#define all(a) (a).begin(), (a).end()

using namespace std;

int nextInt() {int a; cin >> a; return a;}
char nextChar() {char a; cin >> a; return a;}
double nextDouble() {double a; cin >> a; return a;}
string nextString() {string a; cin >> a; return a;}

void inputVector(vector<int> &v, int &n) {rep(i,n){v.push_back(nextInt());}}
void inputVector(vector<double> &v, int &n) {rep(i,n){v.push_back(nextDouble());}}
void inputVector(vector<string> &v, int &n) {rep(i,n){v.push_back(nextString());}}

class Graph {
private:
	// ?????\?????¨??????????????±
	struct QInfo {
		int nodeNum;    // ???????????????
		long long dist;	    // ?????¢

		// ?????????????????????
		QInfo(int argNum, long long argDist) {
			nodeNum = argNum;
			dist = argDist;
		}
		// ??????????????????????????????
		bool operator<(const QInfo& a) const {
			return dist > a.dist;
		}
	};

public:
	// ??¨??????????????±
	struct Edge {
		int next;	    	// ????§????????????????
		long long weight;	// ??¨???????????????

		// ?????????????????????
		Edge() {
			next = -1;
			weight = 0;
		}
		Edge(int argNext, int argWeight) {
			next = argNext;
			weight = argWeight;
		}
	};
	// ?????????????????±
	struct Node {
		long long dist;	    // ????????????????????¨?????¢
		vector<Edge> edge;  // ??\?¶?????????¨???????????±
	};

	// ??????????????????
	vector<Node> node;

	/*
	/  ?????????????????????
	/  - ?????°??§????????????????????°????????????????????????
	*/
	Graph(int num) {
		for (int i = 0; i < num; i++) {
			node.push_back(Node());
		}
	}

	/*
	/  addNode
	/  - ??????????????????
	/   num : ?????????????????°
	*/
	void addNode(int num) {
		for (int i = 0; i < num; i++) {
			node.push_back(Node());
		}
	}

	/*
	/  makeEdge
	/  - ??¨???????????????
	/   prevNode : ??\?¶??????????????????????
	/   nextNode : ??\?¶??????????????????????
	/   weight   : ??¨???????????????
	/   flagBidirect : ??????????????¨??????????????????
	*/
	void makeEdge(int prevNode, int nextNode, long long weight, bool flagBidirect) {
		node[prevNode].edge.push_back(Edge(nextNode, weight));
		if (flagBidirect) {
			node[nextNode].edge.push_back(Edge(prevNode, weight));
		}
	}

	/*
	/  deleteEdge
	/  - ??¨?????????????????????
	/   prevNode : ??\?¶??????????????????????
	/   nextNode : ??\?¶??????????????????????
	/   flagBidirect : ????????????????????¨????????????
	/   ????????? : ?????????????????????????????????
	*/
	bool deleteEdge(int prevNode, int nextNode, bool flagBidirect) {
		bool flagDelete = false;
		vector<Edge>::iterator it;
		// prevNode -> nextNode ?????????
		for (it = node[prevNode].edge.begin(); it != node[prevNode].edge.end(); it++) {
			if ((*it).next == nextNode) {
				node[prevNode].edge.erase(it);
				it--;
				flagDelete = true;
			}
		}

		if (!flagBidirect) return flagDelete;

		// nextNode -> prevNode ?????????
		for (it = node[nextNode].edge.begin(); it != node[nextNode].edge.end(); it++) {
			if ((*it).next == prevNode) {
				node[nextNode].edge.erase(it);
				it--;
				flagDelete = true;
			}
		}

		return flagDelete;
	}

	/*
	/  changeWeight
	/  - ??¨???????????????????????´??????
	/   prevNode : ????§??????????????????????
	/   nextNode : ????§??????????????????????
	/   weight   : ?????´????????????
	/   flagBidirect : ????????????????????¨????????????
	/   ????????? : ?????´???????????????????????????
	*/
	bool changeWeight(int prevNode, int nextNode, long long weight, bool flagBidirect) {
		bool flagChange = false;
		vector<Edge>::iterator it;
		for (it = node[prevNode].edge.begin(); it != node[prevNode].edge.end(); it++) {
			if ((*it).next == nextNode) {
				(*it).weight = weight;
				flagChange = true;
			}
		}

		if (!flagBidirect) return flagChange;

		for (it = node[nextNode].edge.begin(); it != node[nextNode].edge.end(); it++) {
			if ((*it).next == prevNode) {
				(*it).weight = weight;
				flagChange = true;
			}
		}

		return flagChange;
	}

	/*
	/  dijkstra
	/  - ???????????????????????§????????????????????¢????±???????
	/  - startNode??????????????¢??????node???dist???????´??????????
	/  - ?¨???????O((E + V)logV)
	/   startNode : ???????????????????????????
	/   endNode   : ??´????????????????????????
	/   ????????? : 2??????????????¢
	*/
	int dijkstra(int startNode, int endNode) {

		// ?????¢?????????
		for (int i = 0; i < node.size(); i++) {
			node[i].dist = LLONG_MAX;
		}
		node[startNode].dist = 0;

		priority_queue<QInfo> q;
		set<int> inq;
		q.push(QInfo(startNode, 0));
		inq.insert(startNode);
		while (!q.empty()) {
			QInfo now = q.top(); q.pop();
			Node nowNode = node[now.nodeNum];
			inq.erase(now.nodeNum);

			for (vector<Edge>::iterator it = nowNode.edge.begin(); it != nowNode.edge.end(); it++) {
				int nextNode = (*it).next;
				if (nowNode.dist + (*it).weight < node[nextNode].dist) {
					// ?????¢?????´??°
					node[nextNode].dist = nowNode.dist + (*it).weight;

					// ?????\????????\??£??????????????°push
					if (inq.find(nextNode) == inq.end()) {
						q.push(QInfo(nextNode, node[nextNode].dist));
						inq.insert(startNode);
					}
				}
			}
		}

		return node[endNode].dist;
	}

	/*
	/  bellmanFord
	/  - ?????????????????????????????§????????????????????¢????±???????
	/  - startNode??????????????¢??????node???dist???????´??????????
	/  - ???????????????????????°???LLONG_MIN???????´???????
	/  - ?¨???????O(VE)
	/   startNode : ???????????????????????????
	/   endNode   : ??´????????????????????????
	/   ????????? : 2??????????????¢
	*/
	int bellmanFord(int startNode, int endNode) {
		// ?????¢?????????
		for (int i = 0; i < node.size(); i++) {
			node[i].dist = LLONG_MAX;
		}
		node[startNode].dist = 0;

		// ?????????????????????
		for (int i = 0; i < node.size(); i++) {
			for (auto nd : node) {
				if (nd.dist == LLONG_MAX) continue;

				for (auto ed : nd.edge) {
					if (node[ed.next].dist > nd.dist + ed.weight) {
						node[ed.next].dist = nd.dist + ed.weight;
					}
				}
			}
		}

		// ????????????????????§??????
		for (auto nd : node) {
			if (nd.dist == LLONG_MAX) continue;

			for (auto ed : nd.edge) {
				if (node[ed.next].dist > nd.dist + ed.weight) {
					return LLONG_MIN;
				}
			}
		}

		return node[endNode].dist;
	}
};

signed main() {
	while (true) {
		int w, h;
		cin >> w >> h;
		
		if (w == 0) break;

		auto g = Graph(w * h);
		for (int y = 0; y < h - 1; y++) {
			for (int x = 0; x < w; x++) {
				g.makeEdge(y * w + x, (y + 1) * w + x, 1, true);
			}
		}
		for (int y = 0; y < h; y++) {
			for (int x = 0; x < w - 1; x++) {
				g.makeEdge(y * w + x, y * w + x + 1, 1, true);
			}
		}

		int cnt = 0;
		rep(i, h * 2 - 1) {
			int y = i / 2;
			if (i % 2 == 0) {
				rep(x, w - 1) {
					bool input;
					cin >> input;

					if (input) {
						g.deleteEdge(y * w + x, y * w + x + 1, true);
					}
				}
			} else {
				rep(x, w) {
					bool input;
					cin >> input;

					if (input) {
						g.deleteEdge(y * w + x, (y + 1) * w + x, true);
					}
				}
			}
		}

		int dist = g.dijkstra(0, h * w - 1);
		cout << (dist == LLONG_MAX ? 0 : dist + 1) << endl;
	}

    return 0;
}

Measured memory_bytes: 3212