#include "bits/stdc++.h"

#define MOD 1000000007
#define rep(i, n) for(ll i=0; i < (n); i++)
#define rrep(i, n) for(ll i=(n)-1; i >=0; i--)
#define ALL(v) v.begin(),v.end()
#define rALL(v) v.rbegin(),v.rend()
#define FOR(i, j, k) for(ll i=j;i<k;i++)
#define debug_print(var) cerr << #var << "=" << var <<endl;
#define DUMP(i, v)for(ll i=0;i<v.size();i++)cerr<<v[i]<<" "
#define fi first
#define se second

using namespace std;
typedef long long int ll;
typedef vector<ll> llvec;
typedef vector<double> dvec;
typedef pair<ll, ll> P;
typedef long double ld;
struct edge{ll x, c;};

ll mod(ll a, ll mod){
  ll res = a%mod;
  if(res<0)res=res + mod;
  return res;
}

ll modpow(ll a, ll n, ll mod){
  ll res=1;
  while(n>0){
    if(n&1) res=res*a%mod;
    a=a*a%mod;
    n>>=1;
  }
  return res;
}

ll modinv(ll a, ll mod){
  ll b=mod, u=1, v=0;
  while(b){
    ll t=a/b;
    a-=t*b; swap(a, b);
    u-=t*v; swap(u, v);
  }
  u%=mod;
  if(u<0)u+=mod;
  return u;
}

ll gcd(ll a, ll b){
  ll r = a%b;
  if(r==0) return b;
  else return gcd(b, a%b);
}

bool is_prime(ll n){
  ll i = 2;
  if(n==1)return false;
  if(n==2)return true;
  bool res = true;
  while(i*i <n){
    if(n%i==0){
      res = false;
    }
    i = i+1;
  }

  //if(i==1)res = false;
  if(n%i==0)res=false;
  return res;
}

struct UnionFind{
  ll N;
  llvec p;
  llvec cnt;
  UnionFind(ll n){
    N = n;
    p=llvec(N);
    cnt=llvec(N, 0);
    rep(i, N){
      p[i] = i;
      cnt[i] = 1;
    }
  }

  void con(ll a, ll b){
    P at = root(a);
    P bt = root(b);
    if(at.second!=bt.second){
      if(at.first>bt.first){
        swap(at, bt);
        swap(a, b);
      }
      p[at.second] = bt.second;
      cnt[bt.second]+=cnt[at.second];
      p[a]=bt.second;
    }
  }

  P root(ll a){
    ll atmp = a;
    ll c=0;
    while(atmp!=p[atmp]){
      atmp = p[atmp];
      c++;
    }
    p[a] = atmp;
    return {c, atmp};
  }

  bool is_con(ll a, ll b){
    P at=root(a);
    P bt=root(b);
    return at.second == bt.second;
  }
  
};

struct dijkstra{
  ll N;
  llvec d;
  vector<vector<edge>> e;
  dijkstra(ll n){
    N = n;
    //d = llvec(N, 1e18);
    e = vector<vector<edge>>(N);
  }

  void add_edge(ll from, ll to, ll cost){
    e[from].push_back({to, cost});
  }

  void run(ll start){
    priority_queue<P, vector<P>, greater<P>> que;
    que.push({0, start});
    d = llvec(N, 1e18);
    d[start]=0;
    while(!que.empty()){
      P q = que.top();que.pop();
      ll dc = q.first;
      ll x = q.second;
      //cerr << x << " " << dc << endl;
      if(dc>d[x]){
        continue;
      }else{
        for(auto ip: e[x]){
          if(d[ip.x]<=d[x]+ip.c){
            continue;
          }else{
            d[ip.x]= d[x]+ip.c;
            que.push({d[ip.x], ip.x});
          }
        }
      }
    }
  }  
};


/**************************************
** A main function starts from here  **
***************************************/
int main(){
  ll H, W;
  cin >> H >> W;
  vector<string> S(H);
  ll cx,cy;
  ll dx,dy;
  cin >> cx >> cy >> dx >> dy;
  rep(i, H){
    cin >> S[i];
  }

  
  dijkstra dijk(H*W);
  auto ind = [H,W](ll i, ll j){return i*W+j;};
  rep(i, H){
    rep(j, W){
      if(S[i][j]=='#')continue;
      if(i+1<H)if(S[i+1][j]=='.')dijk.add_edge(ind(i, j), ind(i+1, j), 0);
      if(i-1>=0)if(S[i-1][j]=='.')dijk.add_edge(ind(i, j), ind(i-1, j), 0);
      if(j+1<W)if(S[i][j+1]=='.')dijk.add_edge(ind(i, j), ind(i, j+1), 0);
      if(j-1>=0)if(S[i][j-1]=='.')dijk.add_edge(ind(i, j), ind(i, j-1), 0);
      for(ll k=-2;k<=2;k++){
        for(ll l=-2;l<=2;l++){
          if(i+k>=0 and i+k<H and j+l>=0 and j+l<W)if(S[i+k][j+l]=='.')dijk.add_edge(ind(i, j), ind(i+k, j+l), 1);          
        }
      }
      //cerr << i << " "<<j << endl;
    }
  }

  dijk.run(ind(cx-1, cy-1));
  ll ans = dijk.d[ind(dx-1, dy-1)];
  if(ans!=1e18){
    cout << ans;
  }else{
    cout << -1;
  }
  
  return 0;
}


Measured memory_bytes: 206780