#pragma GCC optimize ("O3")
#include <iostream>
#include <iomanip>
#include <istream>
#include <ostream>
#include <sstream>
#include <iterator>
#include <vector>
#include <algorithm>
#include <queue>
#include <deque>
#include <list>
#include <stack>
#include <map>
#include <unordered_map>
#include <set>
#include <bitset>
#include <utility>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <ctime>
#include <cctype>
#include <cstdlib>
#include <numeric>
#define IINF 1000000000
#define INF 3223372036854775807
#define MOD 1000000007
#define mod 1000000007
#define INT_MAX_ 2147483647
#define EPS (1e-10)
#define REP(i, a, n) fo-r (ll i = a; i < (ll)(n); i++)
#define REPE(i, a, n) for (ll i = a; i <= (ll)(n); i++)
//#define rep(i,n)for (ll i = 0; i < (ll)(n); i++)
#define rep(i,l,r)for(ll i=(l);i<(r);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define Endl endl
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define eb emplace_back
#define mmax(x,y)(x>y?x:y)
#define mmin(x,y)(x<y?x:y)
#define chmax(x,y) x=mmax(x,y)
#define chmin(x,y) x=mmin(x,y)
#define all(x) (x).begin(),(x).end()
#define siz(x) (ll)(x).size()
#define PI acos(-1.0)
#define me memset
#define bit(n,k) ((n>>k)&1)
#define lg length()
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;
typedef long double ld;
typedef pair<int,int>Pin;
typedef pair<ll,ll>Pll;
template<class T> using V=vector<T>;
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T> >;
long long GCD(long long a, long long b) {return b?GCD(b,a%b):a;}
long long LCM(long long a, long long b) {return a/GCD(a,b)*b;}
ll pom(ll a,ll n,int m){ll x=1;for(a%=m;n;n/=2)n&1?x=x*a%m:0,a=a*a%m;return x;}
#define invp(a,p)pom(a,p-2,p)
int dx[4]={-1,0,1,0};
int dy[4]={0,-1,0,1};
int ddx[8]={-1,0,1,0,1,1,-1,-1};
int ddy[8]={0,-1,0,1,1,-1,1,-1};
ll cmp1(pair<Pll,ll> a,pair<Pll,ll> b){
        return a.fi.se>b.fi.se;
}
ll cmp2(pair<ll,ll> a,pair<ll,ll> b){
    if(a.se!=b.se)
        return a.se<b.se;
    else
        return a.fi<b.fi;
}
//----------------------------------------------------------------------
ll num[1001][1001];
bool ccolor[1000001];
V<Pll>cal[1000001];
ll magic[1000001];
//----------------------------------------------------------------------
int main(int argc, char * argv[]){
    cin.tie(0);
    ios::sync_with_stdio(false);
    //-------------------------------  
    //ll begin_t=clock();
    //freopen("big.txt", "r", stdin);
    //freopen("out3.txt", "w", stdout);
    //------------------------------
    ll h,w;cin>>h>>w;
    char s[1001][1001];
    ll ch,cw,dh,dw;
    cin>>ch>>cw>>dh>>dw;
    ch--;cw--;dh--;dw--;
    for(ll i=0;i<h;i++){
        for(ll j=0;j<w;j++){
            cin>>s[i][j];
        }
    }
    ll now = 1;
    for(ll i=0;i<h;i++){
        for(ll j=0;j<w;j++){
            if(s[i][j]=='.'&&num[i][j]==0){
                num[i][j]=now;
                queue<Pll>q;
                q.push(mp(i,j));
                while(!q.empty()){
                    Pll p = q.front();q.pop();
                    ll x= p.fi,y=p.se;
                    for(ll i=0;i<4;i++){
                        ll nx = x+dx[i];
                        ll ny = y+dy[i];
                        if(nx>=0&&nx<h&&ny>=0&&ny<w){
                            if(s[nx][ny]=='#')continue;
                            if(num[nx][ny])continue;
                            num[nx][ny]=now;
                            q.push(mp(nx,ny));
                        }
                    }
                }
                now++;
            }
        }
    }
    for(ll i=0;i<h;i++){
        for(ll j=0;j<w;j++){
            if(s[i][j]=='.'){
                cal[num[i][j]].pb({i,j});
            }
        }
    }
    for(ll i=0;i<=1000000;i++)magic[i]=INF;

    now= num[ch][cw];
    queue<ll>C;
    C.push(now);
    magic[now]=0;
    while(!C.empty()){
        bool abc=0;
        ll t = C.front();C.pop();
        for(ll i=0;i<cal[t].size();i++){
            ll x = cal[t][i].fi;
            ll y = cal[t][i].se;
            if(x==dh&&y==dw){
                abc=1;
                break;
            }
            for(ll nx = x-2;nx<=x+2;nx++){
                for(ll ny=y-2;ny<=y+2;ny++){
                    if(nx>=0&&nx<h&&ny>=0&&ny<w){
                        if(s[nx][ny]=='#')continue;
                        if(num[nx][ny]==num[x][y])continue;
                        if(magic[num[nx][ny]]==INF){
                            chmin(magic[num[nx][ny]],magic[num[x][y]]+1);
                            C.push(num[nx][ny]);
                        }
                    }
                }
            }
        }
        if(abc==1)break;
    }
    if(magic[num[dh][dw]]==INF)cout<<-1<<endl;
    else cout<<magic[num[dh][dw]]<<Endl;
    //------------------------------
    //fclose(stdin);
    //fclose(stdout);
    //ll end_t=clock();cout<<"time="<<end_t-begin_t<<"ms"<<endl;
    //------------------------------- 
    return 0;
}
//----------------------------------------------------------------------









































Measured memory_bytes: 55280