/* Aa^~ kokoro ga pyonpyon suru n jaa^~
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*/

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

using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using LL = long long;
using VL = vector<LL>;
using VVL = vector<VL>;
using PLL = pair<LL, LL>;
using VS = vector<string>;

#define ALL(a)  begin((a)),end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

#define FF first
#define SS second

template<class S, class T>
istream& operator>>(istream& is, pair<S,T>& p){
  return is >> p.FF >> p.SS;
}
template<class T>
istream& operator>>(istream& is, vector<T>& xs){
  for(auto& x: xs)
	is >> x;
  return is;
}
template<class S, class T>
ostream& operator<<(ostream& os, const pair<S,T>& p){
  return os << p.FF << " " << p.SS;
}
template<class T>
ostream& operator<<(ostream& os, const vector<T>& xs){
  for(unsigned int i=0;i<xs.size();++i)
	os << (i?" ":"") << xs[i];
  return os;
}
template<class T>
void maxi(T& x, T y){
  if(x < y) x = y;
}
template<class T>
void mini(T& x, T y){
  if(x > y) x = y;
}
void debug(istringstream&){}
template <char sep=',', class Head, class... Tail>
void debug(istringstream& iss, Head&& head, Tail&&... tail)
{
  string name;
  getline(iss, name, ',');
  cout << sep << name << "=" << head;
  debug(iss, forward<Tail>(tail)...);
}

#ifdef PYONPOI
#define DEBUG(...) \
  do{ \
    istringstream ss(#__VA_ARGS__); \
    debug<' '>(ss, __VA_ARGS__); \
    cout<<endl; \
  }while(0)
#else
#define DEBUG
#endif
void init_io(int argc, char* argv[]){
  cin.tie(0);
  ios_base::sync_with_stdio(false);
#ifdef PYONPOI
  if(argc > 1) {
    ifstream *ifs = new ifstream();
    ifs->open(argv[1]);
    cin.rdbuf(ifs->rdbuf());
  }
#endif
}


const double EPS = 1e-10;
const double PI  = acos(-1.0);
const LL MOD = 1e9+7;

int dx[] = {-1, 0, 1, 0};
int dy[] = {0, -1, 0, 1};

int main(int argc, char* argv[]){
  init_io(argc, argv);

  int H, W;
  cin >> H >> W;

  PII S, T;
  cin >> S >> T;
  S.FF--;
  S.SS--;
  T.FF--;
  T.SS--;

  VVI obs(H, VI(W));
  REP(y,H) REP(x,W){
    char c;
    cin >> c;
    obs[y][x] = (c == '#');
  }

  const int INF = 1e9;
  VVI dist(H, VI(W, INF));
  deque<PII> dq;
  dq.push_back(S);
  dist[S.FF][S.SS] = 0;

  auto isin = [&](PII p) {
    return 0 <= p.FF && p.FF < H && 0 <= p.SS && p.SS < W;
  };

  while(!dq.empty()){
    auto p = dq.front();
    dq.pop_front();

    int cur = dist[p.FF][p.SS];

    REP(d,4){
      PII np = p;
      np.FF += dy[d];
      np.SS += dx[d];

      if(!isin(np) || obs[np.FF][np.SS] || dist[np.FF][np.SS] <= cur) continue;
      dist[np.FF][np.SS] = cur;
      dq.push_front(np);
    }

    FOR(ty,-2,2+1) FOR(tx,-2,2+1) {
      PII np = p;
      np.FF += ty;
      np.SS += tx;

      if(!isin(np) || obs[np.FF][np.SS] || dist[np.FF][np.SS] <= cur + 1) continue;
      dist[np.FF][np.SS] = cur + 1;
      dq.push_back(np);
    }
  }

  int ans = dist[T.FF][T.SS];
  if (ans == INF) ans = -1;
  cout << ans << endl;

  return 0;
}


Measured memory_bytes: 11560