#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define pp pair<pair<ll, ll>,pair<ll, ll>>
#define pll pair<ll,ll>
#define ppll pair<ll,pll>
#define pdd pair<double,double>
#define vii vector<int>
#define vll vector<ll>
#define mat vector<vector<ll>>
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define eb emplace_back
#define fi first
#define sc second
#define rep(i,n) for(ll i=0;i<n;i++)
#define rep2(i,a,b) for(ll i=a;i<b;i++)
#define repr(i,n) for(ll i=n-1;i>=0;i--)
#define all(x) x.begin(),x.end()
#define sz(x) (ll) (x).size()
#define pq priority_queue<ll>
#define pqg priority_queue<ll,vector<ll>,greater<ll>>
#define LB(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define UB(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
#define ERASE(v) sort(v.begin(),v.end());v.erase(unique(v.begin(),v.end()),v.end())
#define int ll
// #define ll int
using namespace std;
const ll INF = 1 << 29;
const ll LLINF = (1LL << 60LL);
const ll MOD = 1000000007;
const int MAX_V = 500;
// const ll mod = 998244353;
const ll MAX = 2100000;
const double pi = acos(-1);
const double eps = 1e-10;
ll dx[8] ={1,0,-1,0,1,-1,1,-1};
ll dy[8] ={0,1,0,-1,1,-1,-1,1};
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }




ll H,W;
ll sx,sy,tx,ty;
string s[1010];

struct edge{
    ll to;
    ll cost;
};
vector<edge> G[1000010];
ll d[1000010];


void  dijkstra(int s){
    priority_queue<pii,vector<pii>,greater<pii>> que;
    fill(d,d+1000001,LLINF);
    d[s]=0;
    que.push(pii(0,s));

    while(!que.empty()){
        pii p=que.top();que.pop();
        int v=p.second;
        if(d[v]<p.first) continue;
        rep(i,(ll)G[v].size()){
            edge e=G[v][i];
            if(d[e.to]>d[v]+e.cost){
                d[e.to]=d[v]+e.cost;
                que.push(pii(d[e.to],e.to));
            }
        }
    } 
}




void solve() {
    cin>>H>>W;
    cin>>sx>>sy>>tx>>ty;
    sx--,sy--,tx--,ty--;
    ll S = sx * H + sy;
    ll Go = tx * H + ty;
    rep(i,H) cin>>s[i];
    rep(x,H){
        rep(y,W){
            if(s[x][y] == '#') continue;
            ll index = x * H + y;
            rep2(i,-2,3){
                rep2(j,-2,3){
                    if(i==0&&j==0) continue;
                    ll nx = x + i, ny = y + j;
                    if( nx>=0 && nx <H && ny >=0 && ny < W && s[nx][ny] == '.') {
                        ll to = nx * H + ny;
                        if(abs(i) + abs(j) == 1){
                            G[index].pb({to, 0});
                            // G[to].pb({index, 0});
                        }
                        else {
                            G[index].pb({to, 1});
                            // G[to].pb({index, 1});
                        }
                    }
                    
                }
            }
        }
    }
    dijkstra(S);
    // rep(i,H*W){
    //     cout<<i<<endl;
    //     for(edge j : G[i]){
    //         cout<<j.to<<" "<<j.cost<<", ";
    //     }
    //     cout<<endl;
    // }
    if(d[Go] == LLINF) cout<<-1<<endl;
    else cout<<d[Go]<<endl;


}




signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);


    ll t=1;
    rep(i,t){
        solve(); 
    }


    return 0;
}

Measured memory_bytes: 167728