#include <algorithm>
#include <complex>
#include <cstdlib>
#include <ctime>
#include <time.h>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <numeric>
#include <limits>
#include <type_traits>
#include <locale>
#include <omp.h>

using namespace std;
#define SAY_YES cout << "YES" << endl;
#define SAY_Yes cout << "Yes" << endl;
#define SAY_NO cout << "NO" << endl;
#define SAY_No cout << "No" << endl;
#define IFYES(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "YES" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "NO" << endl;  \
    }
#define IFYes(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "Yes" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "No" << endl;  \
    }
#define IFyes(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "yes" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "no" << endl;  \
    }
#define DEBUG_OUTPUT_ARRAY(XXX, ONE)                            \
    for (int i = 0; i < (ONE); i++)                             \
    {                                                           \
        cout << "DEBUG: i = " << i << " -> " << XXX[i] << endl; \
    }
#define DEBUG_OUTPUT_ARRAY2(XXX, ONE, TWO)                             \
    for (int i = 0; i < (ONE); i++)                                    \
    {                                                                  \
        cout << "<<< i = " << i << " >>>" << endl;                     \
        for (int j = 0; j < (TWO); j++)                                \
        {                                                              \
            cout << "DEBUG: j = " << j << " -> " << XXX[i][j] << endl; \
        }                                                              \
    }
#define DEBUG_OUTPUT_ARRAY2_BOX(XXX, ONE, TWO) \
    for (int i = 0; i < (ONE); i++)            \
    {                                          \
        cout << i << "  ";                     \
        for (int j = 0; j < (TWO); j++)        \
        {                                      \
            cout << XXX[i][j] << " ";          \
        }                                      \
        cout << endl;                          \
    }

typedef pair<long long int, long long int> pll;
typedef pair<long long int, pll> lpll;

const long long int mod = 1000000007;
const long long int INF = 1e18;
const long double PI=3.14159265358979323; 
//const long long int pl=1000000;

long long int H,W,Ch,Dh,Cw,Dw,res[2000][2000]={},sum=0,A[200200],now=0;
char S[2000][2000];
queue<pll>que[1000005];
int main(){
    cout << fixed << setprecision(18);
    cin>>H>>W>>Ch>>Cw>>Dh>>Dw;
    for(long long int i = 1; i <=H; i++){
        for(long long int j = 1; j <= W; j++){
            cin>>S[i][j];
            res[i][j]=INF;
        }
    }
    que[0].push({Ch,Cw});
    res[Ch][Cw]=0;
    while(!que[now].empty()||!que[now+1].empty()){
        if(que[now].empty()){
            now++;
            continue;
        }
        long long tmph=que[now].front().first,tmpw=que[now].front().second;
        if(tmph>=1&&tmph<=H&&tmpw>=1&&tmpw<=W&&now==res[tmph][tmpw]){
            if(S[tmph+1][tmpw]=='.'&&res[tmph+1][tmpw]>res[tmph][tmpw]){
                res[tmph+1][tmpw]=res[tmph][tmpw];
                que[now].push({tmph+1,tmpw});
            }
            if(S[tmph-1][tmpw]=='.'&&res[tmph-1][tmpw]>res[tmph][tmpw]){
                res[tmph-1][tmpw]=res[tmph][tmpw];
                que[now].push({tmph-1,tmpw});
            }
            if(S[tmph][tmpw+1]=='.'&&res[tmph][tmpw+1]>res[tmph][tmpw]){
                res[tmph][tmpw+1]=res[tmph][tmpw];
                que[now].push({tmph,tmpw+1});
            }
            if(S[tmph][tmpw-1]=='.'&&res[tmph][tmpw-1]>res[tmph][tmpw]){
                res[tmph][tmpw-1]=res[tmph][tmpw];
                que[now].push({tmph,tmpw-1});
            }
            
            for(long long int i = max(1LL,tmph-2); i <= min(H,tmph+2) ; i++){
                for(long long int j = max(1LL,tmpw-2); j <= min(W,tmpw+2) ; j++){
                    
                    if(S[i][j]=='.'&&res[i][j]>res[tmph][tmpw]+1){
                        res[i][j]=res[tmph][tmpw]+1;
                        que[now+1].push({i,j});
                    }
                }
            }
        }
        que[now].pop();
    }
    if(res[Dh][Dw]==INF){
        cout<<-1<<endl;
    }else{
        cout<<res[Dh][Dw]<<endl;
    }
    //DEBUG_OUTPUT_ARRAY2_BOX(res,H+1,W+1);
}



Measured memory_bytes: 689476