//#include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;


#include "boost/multiprecision/cpp_int.hpp"
#include "boost/multiprecision/cpp_dec_float.hpp"
namespace mp = boost::multiprecision;
typedef mp::cpp_int LL;
typedef mp::number<mp::cpp_dec_float<1024>> DD;// 仮数部が1024ビットの浮動小数点数型(TLEしたら小さくする)

 
typedef long double dd;
#define i_7 (ll)(1E9+7)
//#define i_7 998244353
#define i_5 i_7-2
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    return c+i_7;
}
typedef pair<ll,ll> l_l;
typedef pair<dd,dd> d_d;
ll inf=(ll)1E16;
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define rrep(i,r,l) for(ll i=r;i>=l;i--)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}
void Max(ll &pos,ll val){pos=max(pos,val);}//Max(dp[n],dp[n-1]);
void Min(ll &pos,ll val){pos=min(pos,val);}
void Add(ll &pos,ll val){pos=mod(pos+val);}
dd EPS=1E-12;
#define fastio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fi first
#define se second
#define endl "\n"  //インタラクティブで消す！！！！！！！！！！！！！！！！！！！！！
#define SORT(v) sort(v.begin(),v.end())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
#define POSL(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define POSU(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
template<class T,class S>
inline bool chmax(T &a, S b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
template<class T,class S>
inline bool chmin(T &a, S b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}

void mod_print(ll k){
    ll P=50000;
    rep(y,1,P){
        ll x=mod(y*k);
        
        if(abs(x)<=P||x+P>=i_7){
            if(x+P>=i_7){
                x-=i_7;
            }
            cout<<x<<"/"<<y<<endl;
            //cout<<setprecision(5)<<(dd)x/(dd)y;
            return;
        }
    }
    cout<<"nun"<<endl;
}
#define all(c) c.begin(),c.end()
typedef vector<ll> vl;
//////////////////////////

ll dx[4]={1,0,-1,0};
ll dy[4]={0,1,0,-1};
ll h,w;
bool valid(ll i,ll j){
    if(0<=i&&i<=h-1&&0<=j&&j<=w-1)return true;
    return false;
}

int main(){fastio
    
    cin>>h>>w;
    ll ch,cw,dh,dw;cin>>ch>>cw>>dh>>dw;
    ch--;cw--;dh--;dw--;
    string s[h];rep(i,0,h-1)cin>>s[i];
    ll d[h][w];rep(i,0,h-1)rep(j,0,w-1)d[i][j]=inf;
    d[ch][cw]=0;
    queue<l_l>q;q.push({ch,cw});
    while(1){
        vector<l_l>v;
        while(!q.empty()){
            l_l t=q.front();q.pop();v.pb(t);
            rep(z,0,3){
                ll nx=t.fi+dx[z];
                ll ny=t.se+dy[z];
                if(!valid(nx,ny))continue;
                if(s[nx][ny]=='#')continue;
                if(chmin(d[nx][ny],d[t.fi][t.se])){
                    q.push({nx,ny});
                }
            }
        }
        for(auto t:v){
            rep(nx,t.fi-2,t.fi+2){
                rep(ny,t.se-2,t.se+2){
                    if(!valid(nx,ny))continue;
                    if(s[nx][ny]=='#')continue;
                    if(chmin(d[nx][ny],1+d[t.fi][t.se])){
                        q.push({nx,ny});
                    }
                }
            }
        }
        if(q.empty())break;
    }
   // rep(i,0,h-1){rep(j,0,w-1)cout<<d[i][j]<<" ";cout<<endl;}
    if(d[dh][dw]>=inf/2)cout<<-1<<endl;
    else cout<<d[dh][dw]<<endl;
    
    return 0;
}


Measured memory_bytes: 12784