// #Sazaの1日1AC
#include<bits/stdc++.h>
using namespace std;
const long long mod=1000000000+7;
const long long INF=9e18;
const double PI=3.14159265358979323846;

//マクロ
//型エイリアス
using ll = long long;
using P=pair<int, int>;
using vl=vector<long long>;
using vvl=vector<vector<long long>>;
using vP=vector<pair<long long, long long>>;
//ショートカット
#define rep(i,n) for(int i = 0; i < n; i++)
#define rep2(i,k,n) for(long long i = k; i < n; i++) //半開区間
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(),v.rend()
#define pb push_back
#define mkp make_pair
//入力
#define vin(v,N) for(long long i=0;i<N;i++) cin>>v.at(i)
#define lin(n) long long n;cin>>n
#define chin(x) char x;cin>>x;
#define sin(s) string s;cin>>s;
#define vlin(v,N) vector<long long>v(N);for(long long i=0;i<N;i++)cin>>v.at(i)

#define max(a,b) max((ll)a,(ll)b)
#define min(a,b) min((ll)a,(ll)b)

//関数
//最大公約数
long long gcd(long long m, long long n){
  long long a=max(m,n);
  long long b=min(m,n);
  long long r=a%b;
  while(r!=0){
    a=b; b=r; r=a%b;
  }
  return b;
}
// 最小公倍数
long long lcd(long long m, long long n){
  return m*n/gcd(m,n);
}
//xのn乗
long long power(long long x, long long N){
  long long ret=1;
  for(long long i=0;i<N;i++)   
    ret*=x;
  return ret;
}
//繰り返し二乗法
long long repeat_squaring(long long x, long long n){
  if(n==0) return 1;
  else if(n%2==0){
    long long t=repeat_squaring(x,n/2);
    return t*t%mod;
  }
  else
    return x*repeat_squaring(x,n-1);
}
//素因数分解(mapで返す)
map<long long,long long> factor(long long p){
  ll p1=p;
  map<long long,long long>ret;
  for(long long i=2;i*i<=p1;i++){
     while(p%i==0){
      ret[i]++;
      p/=i;
    }
  }
  if(p!=1)
  ret[p]++;
  return ret;
}
//素数判定
bool is_prime(long long N){
  for(long long i=2;i*i<=N;i++){
    if(N%i==0)
      return false;
  }
  return true;
}
//最大値更新
void chmax(long long &a,long long b){
  a=max(a,b);
}
//最小値更新
void chmin(long long &a,long long b){
  a=min(a,b);
}

//構造体

//Union-Find木
struct UnionFind{
  //メンバ変数 
  vector<long long>par; //par[i]:=頂点iの親
  vector<long long>s; //s[i]:=頂点iが属する集合の個数(iが根のとき)
  
  //コンストラクタ
  UnionFind(long long N):par(N),s(N){
    for(long long i=0;i<N;i++){
      par[i]=i; //最初はすべてが根として初期化
      s[i]=1;
    }
  }
  //メンバ関数
  //root(i):=頂点iの根
  long long root(long long i){
    if(par[i]==i) return i;
    par[i]=root(par[i]); //経路圧縮
    return root(par[i]); //再帰
  }
  //size[i]:=iが属する集合の個数
  long long size(long long i){
    return s[root(i)];
  }
  //same(x,y) xとyが同じ根を持つか(同じ集合に含まれるか)
  bool same(long long x, long long y){
    return root(x)==root(y);
  }
  //unite(x,y) xの根をyの根に繋げる(集合を合併)
  void unite(long long x, long long y){
    if(!same(x,y)){
      long long rx=root(x);
      long long ry=root(y);
      par[rx]=par[ry];
      s[ry]=s[rx]+s[ry];
    }
  }
};

/////////////////⊂('ω'⊂ )))Σ≡GO!/////////////////
int dh[4] = {1, 0, -1, 0};
int dw[4] = {0, 1, 0, -1};

//メイン関数
int main(){
  //doubleの桁数
  
  int H, W, sh, sw, th, tw;
  cin >> H >> W >> sh >> sw >> th >> tw;
  sh--; th--; sw--; tw--;

  vector<vector<char>> maze(H, vector<char>(W));
  rep(i, H) rep(j, W) cin >> maze[i][j];

  deque<P> Q;

  vector<vector<int>> d(H, vector<int>(W, mod));
  Q.push_front(mkp(sh, sw));
  d[sh][sw] = 0;

  while(!Q.empty()){
    int h, w;
    tie(h, w) = Q.front();
    Q.pop_front();
    //cout << Q.size() << endl;

    rep(i, 4){
      int nh = h + dh[i], nw = w + dw[i];
      if(nh < 0 || H <= nh || nw < 0 || W <= nw) continue;
      if(maze[nh][nw] == '#') continue;
      if(d[nh][nw] <= d[h][w]) continue;
      d[nh][nw] = d[h][w];
      Q.emplace_front(mkp(nh, nw));
    }
    for(int eh = -2; eh <= 2; eh++){
      for(int ew = -2; ew <= 2; ew++){
        int nh = h + eh, nw = w + ew;
        if(nh < 0 || H <= nh || nw < 0 || W <= nw) continue;
        if(maze[nh][nw] == '#') continue;
        if(d[nh][nw] <= d[h][w] + 1) continue;

        d[nh][nw] = d[h][w] + 1;
        Q.emplace_back(mkp(nh, nw));
      }
    }
  }

  if(d[th][tw] == mod) cout << -1 << endl;
  else cout <<d[th][tw] << endl;
}

Measured memory_bytes: 8568