#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
//const int mod = 1e9 + 7;
const int mod = 998244353;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


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 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}


int main() {
  int H, W, Ya, Xa, Yb, Xb;
  cin >> H >> W >> Ya >> Xa >> Yb >> Xb;
  --Ya, --Xa, --Yb, --Xb;
  vector< string > S(H);
  cin >> S;

  assert(1LL * H * W * H * W <= 1e8);
  auto dp = make_v< int >(H, W, H, W);
  fill_v(dp, inf);
  dp[Ya][Xa][Yb][Xb] = 0;
  queue< tuple< int, int, int, int > > que;
  que.emplace(Ya, Xa, Yb, Xb);
  const int vy[] = {-1, 1, 0, 0};
  const int vx[] = {0, 0, -1, 1};
  while(!que.empty()) {
    int a, b, c, d;
    tie(a, b, c, d) = que.front();
    que.pop();
    for(int k = 0; k < 4; k++) {
      int A = a + vy[k];
      int B = b + vx[k];
      if(S[A][B] == '#') continue;
      if(A == c && B == d) continue;
      if(chmin(dp[A][B][c][d], dp[a][b][c][d] + 1)) {
        que.emplace(A, B, c, d);
      }
    }
    for(int k = 0; k < 4; k++) {
      int C = c + vy[k];
      int D = d + vx[k];
      if(S[C][D] == '#') continue;
      if(C == a && D == b) continue;
      if(chmin(dp[a][b][C][D], dp[a][b][c][d] + 1)) {
        que.emplace(a, b, C, D);
      }
    }
  }
  if(dp[Yb][Xb][Ya][Xa] >= inf) cout << -1 << "\n";
  else cout << dp[Yb][Xb][Ya][Xa] << "\n";
}