#line 1 "a.cpp"
#include<iostream>
#include<queue>
using namespace std;
#line 1 "/home/kotatsugame/library/graph/MCF.cpp"
//Minimum Cost Flow O(FE log V)
#include<algorithm>
#include<utility>
#include<vector>
#line 6 "/home/kotatsugame/library/graph/MCF.cpp"
#include<limits>
template<typename T>
struct MCF{
	struct edge{
		int to,rev,cap;
		T cost;
	};
	vector<vector<edge> >G;
	vector<T>h,d;
	vector<int>pv,pe;
	MCF(int n_=0):G(n_),h(n_,0),d(n_),pv(n_),pe(n_){}
	void add_edge(int from,int to,int cap,T cost)
	{
		G[from].push_back({to,(int)G[to].size(),cap,cost});
		G[to].push_back({from,(int)G[from].size()-1,0,-cost});
	}
	T min_cost_flow(int s,int t,int f)//ans or -1
	{
		T ret=0;
		while(f>0)
		{
			priority_queue<pair<T,int>,vector<pair<T,int> >,greater<pair<T,int> > >P;
			fill(d.begin(),d.end(),numeric_limits<T>::max());
			d[s]=0;
			P.push(make_pair(0,s));
			while(!P.empty())
			{
				pair<T,int>p=P.top();P.pop();
				if(d[p.second]<p.first)continue;
				for(int i=0;i<G[p.second].size();i++)
				{
					edge&e=G[p.second][i];
					if(e.cap>0&&d[e.to]>d[p.second]+e.cost+h[p.second]-h[e.to])
					{
						d[e.to]=d[p.second]+e.cost+h[p.second]-h[e.to];
						pv[e.to]=p.second;
						pe[e.to]=i;
						P.push(make_pair(d[e.to],e.to));
					}
				}
			}
			if(d[t]==numeric_limits<T>::max())return -1;
			for(int u=0;u<G.size();u++)h[u]+=d[u];
			int d=f;
			for(int u=t;u!=s;u=pv[u])d=min(d,G[pv[u]][pe[u]].cap);
			f-=d;
			ret+=d*h[t];
			for(int u=t;u!=s;u=pv[u])
			{
				G[pv[u]][pe[u]].cap-=d;
				G[u][G[pv[u]][pe[u]].rev].cap+=d;
			}
		}
		return ret;
	}
};
#line 5 "a.cpp"
int H,W,sx,sy,gx,gy;
string s[1333];
int dist[1333][1333];
int d[5]={0,1,0,-1};
main()
{
	cin>>H>>W>>sx>>sy>>gx>>gy;
	for(int i=0;i<H;i++)cin>>s[i];
	for(int i=0;i<H;i++)for(int j=0;j<W;j++)dist[i][j]=1e9;
	sx--,sy--;
	gx--,gy--;
	dist[sx][sy]=0;
	queue<pair<int,int> >P;
	P.push(make_pair(sx,sy));
	while(!P.empty())
	{
		int x=P.front().first,y=P.front().second;
		P.pop();
		for(int r=0;r<4;r++)
		{
			int tx=x+d[r],ty=y+d[r+1];
			if(s[tx][ty]=='#'||dist[tx][ty]<=dist[x][y]+1)continue;
			dist[tx][ty]=dist[x][y]+1;
			P.push(make_pair(tx,ty));
		}
	}
	if(dist[gx][gy]==(int)1e9)
	{
		cout<<-1<<endl;
		return 0;
	}
	bool fn=false,two=false;
	int x=gx,y=gy;
	while(x!=sx||y!=sy)
	{
		int nx=-1,ny=-1;
		int cnt=0;
		for(int r=0;r<4;r++)
		{
			int tx=x+d[r],ty=y+d[r+1];
			if(s[tx][ty]=='#')continue;
			if(dist[tx][ty]==dist[x][y]-1)
			{
				if(nx<0)nx=tx,ny=ty;
				else two=true;
			}
			cnt++;
		}
		if((x!=gx||y!=gy)&&cnt>=3)fn=true;
		x=nx;
		y=ny;
	}
	if(two)
	{
		cout<<dist[gx][gy]*2<<endl;
		return 0;
	}
	else if(fn)
	{
		cout<<dist[gx][gy]*2+2<<endl;
		return 0;
	}
	MCF<int>F(H*W);
	for(int i=0;i<H;i++)for(int j=0;j<W;j++)if(s[i][j]=='.')
	{
		for(int r=0;r<4;r++)
		{
			int tx=i+d[r],ty=j+d[r+1];
			if(s[tx][ty]=='.')F.add_edge(i*W+j,tx*W+ty,1,1);
		}
	}
	int ans=F.min_cost_flow(sx*W+sy,gx*W+gy,2);
	cout<<ans<<endl;
}