using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
static class Program{
	const int mod=(int)1e9+7;
	static readonly int[][] di1=new int[][]{new int[]{-1,0},new int[]{1,0},new int[]{0,-1},new int[]{0,1}};
	static readonly int[][] di2=new int[][]{new int[]{-1,-1},new int[]{-1,0},new int[]{-1,1},new int[]{0,-1},new int[]{0,1},new int[]{1,-1},new int[]{1,0},new int[]{1,1}};
	static char[][] bm;
	static int[][] b;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.Ia;
		int h=s[0],w=s[1];
		char c='#';
		var t=sc.Ia;
		var g=sc.Ia;
		int sy=t[0],sx=t[1];
		bm=new char[h+2][];
		b=new int[h+2][];
		for(int i = 1;i<=h;i++) {
			bm[i]=(c+sc.S+c).ToCharArray();
			b[i]=new int[w+2];
			for(int j = 0;j<w+2;j++) {
			}
		}
		bm[0]=bm[h+1]=new string(c,w+2).ToCharArray();
		b[0]=b[h+1]=new int[w+2];
		var pq=new Rheap<ValueTuple<int,int>>(32);
		pq.Push(new Rheap<ValueTuple<int,int>>.Dt(1,ValueTuple.Create(sy,sx)));
		b[sy][sx]=1;
		while(pq.cnt>0){
			var e=pq.Dequeue;
			Fdi(e.d.Item1,e.d.Item2,(y,x)=>{
				if(bm[y][x]=='.'&&(b[y][x]==0||b[y][x]>e.n)){
					pq.Push(new Rheap<ValueTuple<int,int>>.Dt(e.n,ValueTuple.Create(y,x)));
					b[y][x]=(int)e.n;
				}
			});
			for(int i = -2;i<=2;i++) {
				for(int j = -2;j<=2;j++) {
					int y=e.d.Item1+i;
					int x=e.d.Item2+j;
					if(y>0&&x>0&&y<=s[0]&&x<=s[1]&&bm[y][x]=='.'&&b[y][x]==0){
						pq.Push(new Rheap<ValueTuple<int,int>>.Dt(e.n+1,ValueTuple.Create(y,x)));
						b[y][x]=(int)e.n+1;
					}
				}
			}
		}
		Console.WriteLine("{0}",b[g[0]][g[1]]-1);
	}
	static void Fdi(int y,int x,Action<int,int> f){for(int i=0;i<4;i++){f(y+di1[i][0],x+di1[i][1]);}}
}
public class Rheap<T>{
	public class Dt{
		public long n;
		public T d;
		public Dt(long n,T d){this.n=n;this.d=d;}
		public override string ToString()=>"d:"+d.ToString()+" n:"+n.ToString();
	}
	private const int m=65;
	private long la=0;
	private Dt[][] bf;
	private int[] h;
	public int cnt=0;
	public Rheap(int max){
		bf=new Dt[m][];
		h=new int[m];
		for(int i = 0;i<m;i++) {bf[i]=new Dt[max];}
	}
	public void Push(Dt x){
		int a=x.n!=la?Bsr(la^x.n)+1:0;
		if(h[a]==bf[a].Length){Extend(a);}
		bf[a][h[a]]=x;
		cnt++;
		h[a]++;
	}
	public Dt Peek{get{
		if(h[0]==0){
			for(int i = 1;i<m;i++) {
				if(h[i]>0){
					int p=0;
					for(int j = 1;j<h[i];j++) {
						if(bf[i][p].n>bf[i][j].n){p=j;}
					}
					la=bf[i][p].n;
					for(int j = 0;j<h[i];j++) {
						Push(bf[i][j]);
						cnt--;
					}
					h[i]=0;
					break;
				}
			}
		}
		return bf[0][h[0]-1];
	}}
	public Dt Dequeue{get{
		var e=Peek;
		h[0]--;
		cnt--;
		return e;
	}}
	private void Extend(int n){
		var nhe=new Dt[bf[n].Length<<1];
		Array.Copy(bf[n],nhe,bf[n].Length);
		bf[n]=nhe;
	}
	private int Bsr(long b){
		int n=0;
		if(b==0){return -1;}
		if((b&-4294967296)!=0){b=b&-4294967296;n+=32;}
		if((b&-281470681808896)!=0){b=b&-281470681808896;n+=16;}
		if((b&-71777214294589696)!=0){b=b&-71777214294589696;n+=8;}
		if((b&-1085102592571150096)!=0){b=b&-1085102592571150096;n+=4;}
		if((b&-3689348814741910324)!=0){b=b&-3689348814741910324;n+=2;}
		if((b&-6148914691236517206)!=0){b=b&-6148914691236517206;n+=1;}
		return n;
	}
}
public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}

Measured memory_bytes: 54184