#include <stdio.h>
#include <bits/stdc++.h>

#include <algorithm>
#include <cassert>
#include <limits>
#include <queue>
#include <vector>

namespace atcoder {

template <class Cap, class Cost> struct mcf_graph {
  public:
    mcf_graph() {}
    mcf_graph(int n) : _n(n), g(n) {}

    int add_edge(int from, int to, Cap cap, Cost cost) {
        assert(0 <= from && from < _n);
        assert(0 <= to && to < _n);
        int m = int(pos.size());
        pos.push_back({from, int(g[from].size())});
        g[from].push_back(_edge{to, int(g[to].size()), cap, cost});
        g[to].push_back(_edge{from, int(g[from].size()) - 1, 0, -cost});
        return m;
    }

    struct edge {
        int from, to;
        Cap cap, flow;
        Cost cost;
    };

    edge get_edge(int i) {
        int m = int(pos.size());
        assert(0 <= i && i < m);
        auto _e = g[pos[i].first][pos[i].second];
        auto _re = g[_e.to][_e.rev];
        return edge{
            pos[i].first, _e.to, _e.cap + _re.cap, _re.cap, _e.cost,
        };
    }
    std::vector<edge> edges() {
        int m = int(pos.size());
        std::vector<edge> result(m);
        for (int i = 0; i < m; i++) {
            result[i] = get_edge(i);
        }
        return result;
    }

    std::pair<Cap, Cost> flow(int s, int t) {
        return flow(s, t, std::numeric_limits<Cap>::max());
    }
    std::pair<Cap, Cost> flow(int s, int t, Cap flow_limit) {
        return slope(s, t, flow_limit).back();
    }
    std::vector<std::pair<Cap, Cost>> slope(int s, int t) {
        return slope(s, t, std::numeric_limits<Cap>::max());
    }
    std::vector<std::pair<Cap, Cost>> slope(int s, int t, Cap flow_limit) {
        assert(0 <= s && s < _n);
        assert(0 <= t && t < _n);
        assert(s != t);
        // variants (C = maxcost):
        // -(n-1)C <= dual[s] <= dual[i] <= dual[t] = 0
        // reduced cost (= e.cost + dual[e.from] - dual[e.to]) >= 0 for all edge
        std::vector<Cost> dual(_n, 0), dist(_n);
        std::vector<int> pv(_n), pe(_n);
        std::vector<bool> vis(_n);
        auto dual_ref = [&]() {
            std::fill(dist.begin(), dist.end(),
                      std::numeric_limits<Cost>::max());
            std::fill(pv.begin(), pv.end(), -1);
            std::fill(pe.begin(), pe.end(), -1);
            std::fill(vis.begin(), vis.end(), false);
            struct Q {
                Cost key;
                int to;
                bool operator<(Q r) const { return key > r.key; }
            };
            std::priority_queue<Q> que;
            dist[s] = 0;
            que.push(Q{0, s});
            while (!que.empty()) {
                int v = que.top().to;
                que.pop();
                if (vis[v]) continue;
                vis[v] = true;
                if (v == t) break;
                // dist[v] = shortest(s, v) + dual[s] - dual[v]
                // dist[v] >= 0 (all reduced cost are positive)
                // dist[v] <= (n-1)C
                for (int i = 0; i < int(g[v].size()); i++) {
                    auto e = g[v][i];
                    if (vis[e.to] || !e.cap) continue;
                    // |-dual[e.to] + dual[v]| <= (n-1)C
                    // cost <= C - -(n-1)C + 0 = nC
                    Cost cost = e.cost - dual[e.to] + dual[v];
                    if (dist[e.to] - dist[v] > cost) {
                        dist[e.to] = dist[v] + cost;
                        pv[e.to] = v;
                        pe[e.to] = i;
                        que.push(Q{dist[e.to], e.to});
                    }
                }
            }
            if (!vis[t]) {
                return false;
            }

            for (int v = 0; v < _n; v++) {
                if (!vis[v]) continue;
                // dual[v] = dual[v] - dist[t] + dist[v]
                //         = dual[v] - (shortest(s, t) + dual[s] - dual[t]) + (shortest(s, v) + dual[s] - dual[v])
                //         = - shortest(s, t) + dual[t] + shortest(s, v)
                //         = shortest(s, v) - shortest(s, t) >= 0 - (n-1)C
                dual[v] -= dist[t] - dist[v];
            }
            return true;
        };
        Cap flow = 0;
        Cost cost = 0, prev_cost = -1;
        std::vector<std::pair<Cap, Cost>> result;
        result.push_back({flow, cost});
        while (flow < flow_limit) {
            if (!dual_ref()) break;
            Cap c = flow_limit - flow;
            for (int v = t; v != s; v = pv[v]) {
                c = std::min(c, g[pv[v]][pe[v]].cap);
            }
            for (int v = t; v != s; v = pv[v]) {
                auto& e = g[pv[v]][pe[v]];
                e.cap -= c;
                g[v][e.rev].cap += c;
            }
            Cost d = -dual[s];
            flow += c;
            cost += c * d;
            if (prev_cost == d) {
                result.pop_back();
            }
            result.push_back({flow, cost});
            prev_cost = cost;
        }
        return result;
    }

  private:
    int _n;

    struct _edge {
        int to, rev;
        Cap cap;
        Cost cost;
    };

    std::vector<std::pair<int, int>> pos;
    std::vector<std::vector<_edge>> g;
};

}  // namespace atcoder

using namespace atcoder;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000

int H,W;
vector<string> S;
vector<int> dy = {0,0,1,-1},dx = {1,-1,0,0};
vector<vector<int>> get(int r,int c){
	queue<pair<int,int>> Q;
	vector<vector<int>> dis(H,vector<int>(W,Inf));
	dis[r][c] = 0;
	Q.emplace(r,c);
	
	
	while(Q.size()>0){
		int y = Q.front().first,x = Q.front().second;
		Q.pop();
		
		rep(i,4){
			int yy = y+dy[i],xx = x+dx[i];
			if(yy<0||yy>=H||xx<0||xx>=W)continue;
			if(S[yy][xx]=='#')continue;
			if(dis[yy][xx]!=Inf)continue;
			dis[yy][xx] = dis[y][x]+1;
			Q.emplace(yy,xx);
		}
	}
	
	return dis;
}

int main(){
	
	cin>>H>>W;
	S.resize(H);
	int r0,c0,r1,c1;
	cin>>r0>>c0>>r1>>c1;
	r0--,c0--,r1--,c1--;
	rep(i,H){
		cin>>S[i];
	}
	
	auto d0 = get(r0,c0),d1 = get(r1,c1);
	
	if(d0[r1][c1]==Inf)cout<<-1<<endl;
	else{
		int D = d0[r1][c1];
		int cnt = 0;
		rep(i,H){
			rep(j,W){
				if(d0[i][j] + d1[i][j]==D)cnt++;
			}
		}
		
		if(cnt>D+1){
			cout<<2*D<<endl;
			return 0;
		}
		else{
			rep(i,H){
				rep(j,W){
					if(d0[i][j]==Inf)continue;
					if(d0[i][j]+d1[i][j]==D)continue;
					rep(k,4){
						int ii = i+dy[k],jj = j+dx[k];
						if(d0[ii][jj]+d1[ii][jj]==D && d0[ii][jj]!=0 && d1[ii][jj]!=0){
							cout<<2*D+2<<endl;
							return 0;
						}
					}
					
				}
			}
		}
		
		mcf_graph<int,int> G(2*H*W);
		rep(i,H){
			rep(j,W){
				if(S[i][j]=='#')continue;
				G.add_edge(2*(i*W+j),2*(i*W+j)+1,1,0);
				rep(k,4){
					int ii = i,jj = j;
					ii += dy[k],jj += dx[k];
					if(S[ii][jj]=='#')continue;
					
					G.add_edge(2*(i*W+j)+1,2*(ii*W+jj),1,1);
				}
			}
		}
		cout<<-1<<endl;
		/*
		auto ans = G.flow(2*(r0*W+c0)+1,2*(r1*W+c1),2);
		if(ans.first<2)cout<<-1<<endl;
		else cout<<ans.second<<endl;
		*/
		
	}
	
    return 0;
}