//#define _GLIBCXX_DEBUG

#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T1, typename T2>bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++){cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++){for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>vector<vector<T>>vec(ll x, ll y, T w){vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v(ts...))>(a,make_v(ts...));}
template<typename T1, typename T2>ostream &operator<<(ostream &os, const pair<T1, T2>&p){return os << p.first << " " << p.second;}
template<typename T>ostream &operator<<(ostream &os, const vector<T> &v){for(auto &z:v)os << z << " ";cout<<"|"; return os;}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
struct z{
  ll x,y,d;
  z(ll a,ll b,ll c):x(a),y(b),d(c){};
};
vector<vector<ll>>dist(1005,vector<ll>(1005,INF));
void bfs(ll h,ll w,vector<string>&a,ll ax,ll ay){
  rep(i,0,h)rep(j,0,w)dist[i][j]=INF;
  deque<struct z>que;
  que.emplace_front(ax,ay,0);
  while(!que.empty()){
    auto pos = que.front();
    que.pop_front();
    if(dist[pos.x][pos.y]!=INF||a[pos.x][pos.y]=='#')continue;
    dist[pos.x][pos.y]=pos.d;
    for(ll i=0;i<4;i++){
      ll x=pos.x+dx[i],y=pos.y+dy[i],d=pos.d;
      if(x<0||x>=h||y<0||y>=w)continue;
      que.emplace_front(x,y,d);
    }
    rep(i,-2,3)rep(j,-2,3){
      ll x=pos.x+i,y=pos.y+j,d=pos.d+1;
      if(x<0||x>=h||y<0||y>=w)continue;
      que.emplace_back(x,y,d);
    }
  }
}
int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll h,w;cin>>h>>w;
  ll ch,cw;cin>>ch>>cw;ch--;cw--;
  ll dh,dw;cin>>dh>>dw;dh--;dw--;
  vector<string>s(h);
  rep(i,0,h)cin>>s[i];
  bfs(h,w,s,ch,cw);
  ans(dist[dh][dw]==INF,-1,dist[dh][dw]);
  return 0;
}

Measured memory_bytes: 18912