//#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;}
template<typename T>void rearrange(vector<ll>&ord, vector<T>&v){
  auto tmp = v;
  for(int i=0;i<tmp.size();i++)v[i] = tmp[ord[i]];
}
template<typename Head, typename... Tail>void rearrange(vector<ll>&ord,Head&& head, Tail&&... tail){
  rearrange(ord, head);
  rearrange(ord, tail...);
}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
int popcount(ll x){return __builtin_popcountll(x);};
int poplow(ll x){return __builtin_ctzll(x);};
int pophigh(ll x){return 63 - __builtin_clzll(x);};

int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll h,w,ra,ca,rb,cb;cin>>h>>w>>ra>>ca>>rb>>cb;ra--;ca--;rb--;cb--;
  vector<string>s(h);
  rep(i,0,h){
    cin>>s[i];
  }
  vector<vector<int>>dist;
  vector<vector<int>>dp;
  bool ok=true;
  auto solve=[&](){
    queue<P>que;
    dist=vec(h,w,-1);
    dp=vec(h,w,0);
    que.emplace(ra,ca);
    dist[ra][ca]=0;
    dp[ra][ca]=1;
    while(!que.empty()){
      auto p=que.front();
      que.pop();
      ll d=dist[p.fi][p.se];
      rep(i,0,4){
        ll x=p.fi+dx[i],y=p.se+dy[i];
        if(x<0||y<0||x>=h||y>=w||s[x][y]=='#')continue;
        if(!ok&&p.fi==ra&&p.se==ca&&x==rb&&y==cb)continue;
        if(dist[x][y]==-1){
          dist[x][y]=d+1;
          dp[x][y]=dp[p.fi][p.se];
          que.emplace(x,y);
        }
        else if(dist[x][y]==d+1)dp[x][y]=min(2,dp[x][y]+dp[p.fi][p.se]);
      }
    }
  };

  ll ret=INF;
  solve();
  auto dpre=dist;
  //debug(dist,h,w);cout<<endl;
  //debug(dp,h,w);cout<<endl;
  if(dist[rb][cb]==-1){
    cout<<-1<<endl;
    return 0;
  }
  vector<P>path;
  {
    ll nx=rb,ny=cb;
    while(nx!=ra||ny!=ca){
      rep(i,0,4){
        ll x=nx+dx[i],y=ny+dy[i];
        if(x<0||y<0||x>=h||y>=w||dist[x][y]+1!=dist[nx][ny])continue;
        path.EB(x,y);
        nx=x;ny=y;
        break;
      }
    }
    path.pop_back();
  }
  for(auto z:path){
    ll cnt=0;
    rep(i,0,4){
      ll x=z.fi+dx[i],y=z.se+dy[i];
      if(x<0||y<0||x>=h||y>=w||s[x][y]=='#')continue;
      cnt++;
    }
    if(cnt>=3)chmin(ret,dist[rb][cb]*2+2);
  }
  if(dp[rb][cb]>=2)chmin(ret,dist[rb][cb]*2);
  //cout<<ret spa dist[rb][cb]<<endl;
  ll dd=dist[rb][cb];
  {
    for(auto z:path){
      s[z.fi][z.se]='#';
    }
    ok=false;
    solve();
    ok=true;
    //debug(s,h,w);cout<<endl;
    //debug(dist,h,w);cout<<endl;
    //debug(dp,h,w);cout<<endl;
    //cout<<dd spa dist[rb][cb]<<endl;
    if(dist[rb][cb]!=-1)chmin(ret,dist[rb][cb]+dd);
    for(auto z:path){
      s[z.fi][z.se]='.';
    }
  }
  {
    swap(ra,rb);swap(ca,cb);
    solve();
    swap(ra,rb);swap(ca,cb);
    //debug(dist,h,w);
    rep(i,0,h)rep(j,0,w){
      if(dpre[i][j]==-1||dist[i][j]==-1)continue;
      ll cnt=0;
      rep(o,0,4){
        ll x=i+dx[o],y=j+dy[o];
        if(x<0||y<0||x>=h||y>=w||s[x][y]=='#')continue;
        cnt++;
      }
      //cout<<i spa j spa cnt<<endl;
      if(cnt>=3)chmin(ret,(dpre[i][j]+dist[i][j])*2+4);
    }
  }
  ans(ret==INF,-1,ret);
  return 0;
}