/*****Author: Satyajeet Singh************************************/
    import java.io.*;
    import java.util.*;
    import java.text.*; 
    import java.lang.*;
    import java.math.*;
public class Main{
/*********************************************Constants******************************************/
    static PrintWriter out=new PrintWriter(new OutputStreamWriter(System.out));        
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static long mod=(long)1e9+7;
    static long mod1=998244353;
    static ArrayList<Integer> graph[];
    static int pptr=0,pptrmax=0;
    static String st[];
/*****************************************Solution Begins***************************************/    
    
    public static void main(String args[]) throws Exception{      
        int n=pi();
        int m=pi();
        int sx=pi()-1;
        int sy=pi()-1;
        int ex=pi()-1;
        int ey=pi()-1;

        boolean input[][]=new boolean[n][m];

        for(int i=0;i<n;i++){
            String str=ps();
            for(int j=0;j<m;j++){
                if(str.charAt(j)=='.')input[i][j]=true;
            }
        }
        Deque<Pair> dq=new ArrayDeque<>();
        dq.add(new Pair(sx,sy));
        long dist[][]=new long[n][m];
        for(long ar[]:dist)
            Arrays.fill(ar,Integer.MAX_VALUE/2);
        int dx[]={1,-1,0,0};
        int dy[]={0,0,-1,1};
        dist[sx][sy]=0;

        while(!dq.isEmpty()){
            Pair p=dq.removeFirst();
            int x=p.u;
            int y=p.v;
            for(int k=0;k<4;k++){
                int xx=x+dx[k];
                int yy=y+dy[k];
                if(xx>=n||yy>=m||xx<0||yy<0||!input[xx][yy]||dist[xx][yy]<=dist[x][y])
                    continue;
                dist[xx][yy]=dist[x][y];
                dq.addFirst(new Pair(xx,yy));
            }            
            for(int i=-2;i<=2;i++){
                for(int j=-2;j<=2;j++){
                    int xx=x+i;
                    int yy=y+j;
                    if(xx>=n||yy>=m||xx<0||yy<0||!input[xx][yy]||dist[xx][yy]<=dist[x][y]+1)
                        continue;
                    dist[xx][yy]=dist[x][y]+1;
                    dq.addLast(new Pair(xx,yy));
                }
            }
        }
        long ans=dist[ex][ey];
        if(ans>=Integer.MAX_VALUE/3)ans=-1;
        out.println(ans);
/****************************************Solution Ends**************************************************/
        clr();
    }
    static void clr(){
        out.flush();
        out.close();
    }
    static void nl() throws Exception{
        pptr=0;
        st=br.readLine().split(" ");
        pptrmax=st.length;
    }
    static void nls() throws Exception{
        pptr=0;
        st=br.readLine().split("");
        pptrmax=st.length;
    }
    static int pi() throws Exception{
        if(pptr==pptrmax)
            nl();
        return Integer.parseInt(st[pptr++]);
    }
    static long pl() throws Exception{
        if(pptr==pptrmax)
            nl();
        return Long.parseLong(st[pptr++]);
    }
    static double pd() throws Exception{
        if(pptr==pptrmax)
            nl();
        return Double.parseDouble(st[pptr++]);
    }
    static String ps() throws Exception{
        if(pptr==pptrmax)
            nl();
        return st[pptr++];
    }
/***************************************Precision Printing**********************************************/
    static void printPrecision(double d){
        DecimalFormat ft = new DecimalFormat("0.00000000000"); 
        out.println(ft.format(d));
    }
/**************************************Bit Manipulation**************************************************/
    static int countBit(long mask){
        int ans=0;
        while(mask!=0){
            mask&=(mask-1);
            ans++;
        }
        return ans;
    }
/******************************************Graph*********************************************************/
    static void Makegraph(int n){
        graph=new ArrayList[n];
        for(int i=0;i<n;i++)
            graph[i]=new ArrayList<>();
    }
    static void addEdge(int a,int b){
        graph[a].add(b);
    }
    // static void addEdge(int a,int b,int c){
    //     graph[a].add(new Pair(b,c));
    // }    
/*********************************************PAIR********************************************************/
    static class Pair{
        int u;
        int v;
        public Pair(int u, int v) {
            this.u = u;
            this.v = v;
        }
        public int hashCode() {
            int hu = (int) (u ^ (u >>> 32));
            int hv = (int) (v ^ (v >>> 32));
            return 31 * hu + hv;
        }
        public boolean equals(Object o) {
            Pair other = (Pair) o;
            return u == other.u && v == other.v;
        }
        public String toString() {
            return "[u=" + u + ", v=" + v + "]";
        }
    }
/******************************************Long Pair*******************************************************/
    static class Pairl{
        long u;
        long v;
        public Pairl(long u, long v) {
            this.u = u;
            this.v = v;
        }
        public int hashCode() {
            int hu = (int) (u ^ (u >>> 32));
            int hv = (int) (v ^ (v >>> 32));
            return 31 * hu + hv;
        }
        public boolean equals(Object o) {
            Pairl other = (Pairl) o;
            return u == other.u && v == other.v;
        }
        public String toString() {
            return "[u=" + u + ", v=" + v + "]";
        }
    }
/*****************************************DEBUG***********************************************************/
    public static void debug(Object... o){
        System.out.println(Arrays.deepToString(o));
    }
/************************************MODULAR EXPONENTIATION***********************************************/
    static long modulo(long a,long b,long c){
        long x=1,y=a%c;
        while(b > 0){
            if(b%2 == 1)
                x=(x*y)%c;
            y = (y*y)%c;
            b = b>>1;
        }
        return  x%c;
    }
/********************************************GCD**********************************************************/
    static long gcd(long x, long y){
        if(x==0)
            return y;
        if(y==0)
            return x;
        long r=0, a, b;
        a = (x > y) ? x : y; 
        b = (x < y) ? x : y;
        r = b;
        while(a % b != 0){
            r = a % b;
            a = b;
            b = r;
        }
        return r;
    }
}

Measured memory_bytes: 54256