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

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define bit(n) (1LL<<(n))
#define F first
#define S second
// functions
template <typename T> void unique(T& c){c.erase(std::unique(c.begin(), c.end()), c.end());}
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 60;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

string s[1010];
int res[1010][1010];

bool in(int x, int y, int h, int w){
  return (x >= 0) && (x < h) && (y >= 0) && (y < w);
}

int main(int argc, char const* argv[])
{
  int h, w; cin >> h >> w;
  int ch, cw; cin >> ch >> cw; ch--; cw--;
  int dh, dw; cin >> dh >> dw; dh--; dw--;
  rep(i, h)cin >> s[i];
  using pt = pair<int, P>;
  priority_queue<pt, vector<pt>, greater<pt>> pq;
  rep(i, h){
    rep(j, w)res[i][j] = inf;
  }
  res[ch][cw] = 0;
  pq.push(mk(0, mk(ch, cw)));
  while(!pq.empty()){
    auto p = pq.top(); pq.pop();
    int d = p.first, x = p.second.first, y = p.second.second;
    if(res[x][y] < d)continue;
    rep(k, 4){
      int nx = x + dx[k];
      int ny = y + dy[k];
      if(in(nx, ny, h, w) && s[nx][ny] != '#' && res[nx][ny] > d){
        res[nx][ny] = d;
        pq.push(mk(d, mk(nx, ny)));
      }
    }
    for(int i = -2; i <= 2; i++){
      for(int j = -2; j <= 2; j++){
        if(i == 0 && j == 0)continue;
        int nx = i + x, ny = j + y;
      if(in(nx, ny, h, w) && s[nx][ny] != '#' && res[nx][ny] > d + 1){
        res[nx][ny] = d + 1;
        pq.push(mk(d + 1, mk(nx, ny)));
      }
      }
    }
  }
  if(res[dh][dw] == inf)cout << -1 << endl;
  else cout << res[dh][dw] << endl;
  return 0;
}


Measured memory_bytes: 8700