#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define all(a) (a).begin(), (a).end()
template<typename T = int> using V = vector<T>;
template<typename T = int> using P = pair<T, T>;
using Vi = V<int>;
using Vl = V<ll>;
using Vd = V<ld>;
using VVi = V<Vi>;
using VVl = V<Vl>;
using VVd = V<Vd>;
using Pi = P<int>;
using Pl = P<ll>;
using Pd = P<ld>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<typename T> inline int sz(T &x) { return x.size(); }
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << '(' << p.first << ", " << p.second << ')'; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<typename T> inline int count_between(vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
inline int fLog2(const ll x) { assert(x > 0); return 63-__builtin_clzll(x); } // floor(log2(x))
inline int cLog2(const ll x) { assert(x > 0); return (x == 1) ? 0 : 64-__builtin_clzll(x-1); } // ceil(log2(x))
inline int popcount(const ll x) { return __builtin_popcountll(x); }
inline void fail() { cout << -1 << '\n'; exit(0); }
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
const int INF  = 1<<30;
// const ll INFll = 1ll<<60;
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
// const int MOD  = int(1e9)+7;
// const int MOD  = 998244353;


const Vi dx = {1, 0, -1, 0};
const Vi dy = {0, 1, 0, -1};


int main() {
  ll h, w; cin >> h >> w;
  int si, sj; cin >> si >> sj;
  int ti, tj; cin >> ti >> tj;
  --si, --sj, --ti, --tj;

  vector<string> field(h);
  rep(i, h) cin >> field[i];

  auto dist = make_vec(h, w, INF);
  deque<Pi> que;
  dist[si][sj] = 0;
  que.emplace_back(si, sj);
  
  while (!que.empty()) {
    auto [i, j]  = que.front(); que.pop_front();
    rep(dir, sz(dx)) {
      int ii = i + dx[dir];
      int jj = j + dy[dir];
      if (ii < 0 || ii >= h || jj < 0 || jj >= w) continue;
      if (field[ii][jj] == '#') continue;
      if (chmin(dist[ii][jj], dist[i][j])) {
        que.emplace_front(ii, jj);
      }
    }

    rep2(di, -2, 3) rep2(dj, -2, 3) {
      if (abs(di) + abs(dj) <= 1) continue;
      int ii = i + di;
      int jj = j + dj;
      if (ii < 0 || ii >= h || jj < 0 || jj >= w) continue;
      if (field[ii][jj] == '#') continue;
      if (chmin(dist[ii][jj], dist[i][j] + 1)) {
        que.emplace_back(ii, jj);
      }
    }
  }


  ll ans = dist[ti][tj];
  if (ans == INF) ans = -1;
  cout << ans << '\n';
}


Measured memory_bytes: 8796