#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <tuple>
#include <utility>
#include <vector>
#define ll long long
#define itn int
#define endl '\n'
#define co(ans) cout<<ans<<endl
#define COYE cout<<"YES"<<endl
#define COYe cout<<"Yes"<<endl
#define COye cout<<"yes"<<endl
#define CONO cout<<"NO"<<endl
#define CONo cout<<"No"<<endl
#define COno cout<<"no"<<endl
#define FORE(i,a) for(auto &i:a)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FFOR(i,a,b) for(int i=(a);i<=(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n)  FFOR(i,1,n)
#define PB push_back
#define MP make_pair
#define ALL(V) (V).begin(),(V).end()
#define SORT(V) sort((V).begin(),(V).end())
#define REVERSE(V) reverse((V).begin(),(V).end())
#define EACH(V,i) for(typeof((V).begin()) i=(V).begin();i!=(V).end();++i)
#define equals(a,b) (fabs((a)-(b))<EPS)
#define INF ((1LL<<62)-(1LL<<31))
#define EPS 1e-10
#define PI 3.141592653589793238
#define MOD 1000000007
#define MMOD 998244353
#define MAX 2010101
using namespace std;
using Edge=pair<ll,ll>;
using Graph=vector<vector<int>>;
inline int toInt(string s){int v;istringstream sin(s);sin>>v;return v;}
template<class T>inline string toString(T x){ostringstream sout;sout<<x;return sout.str();}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return 1;}return 0;}
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
const int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

int main(){
  ll H,W,CH,CW,DH,DW;
  cin>>H>>W>>CH>>CW>>DH>>DW;
  char S[H+1][W+1];
  REP(i,H+1){
    REP(j,W+1){
      if(i==0 || j==0) S[i][j]='#';
      else cin>>S[i][j];
    }
  }
  
  queue<pair<ll,ll>> Q,NEXT;
  Q.push(MP(CH,CW));
  bool SEEN[H+1][W+1];
  ll DIS[H+1][W+1];
  REP(i,H+1){
    REP(j,W+1){
      SEEN[i][j]=false;
      DIS[i][j]=INF;
    }
  }
  SEEN[CH][CW]=true;
  DIS[CH][CW]=0;
  
  ll roop=0;
  while(1!=0){
    auto v=Q.front();
    Q.pop();
    NEXT.push(MP(v.first,v.second));
    REP(i,4){
      ll vy=v.first+dy[i],vx=v.second+dx[i];
      if(vy<=0 || vx<=0 || vy>H || vx>W) continue;
      if(SEEN[vy][vx]) continue;
      if(S[vy][vx]=='#') continue;
      SEEN[vy][vx]=true;
      DIS[vy][vx]=roop;
      Q.push(MP(vy,vx));
      NEXT.push(MP(vy,vx));
    }
    
    if(Q.empty()){
      roop++;
      while(!NEXT.empty()){
        auto u=NEXT.front();
        NEXT.pop();
        for(int I=u.first-2; I<=u.first+2; ++I){
          for(int J=u.second-2; J<=u.second+2; ++J){
            if(I<=0 || J<=0 || I>H || J>W) continue;
            if(SEEN[I][J]==false && S[I][J]!='#'){
              Q.push(MP(I,J));
              SEEN[I][J]=true;
              DIS[I][J]=roop;
            }
          }
        }
      }
      if(Q.empty()){
        ll ans=DIS[DH][DW];
        if(ans==INF) ans=-1;
        cout<<ans<<endl;
        return 0;
      }
    }
    
  }
  
  return 0;
}

Measured memory_bytes: 13568