#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/mincostflow>
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;
}