#define MOD_TYPE 2

#pragma region Macros
#include <bits/stdc++.h>
using namespace std;
/*
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using Int = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
*/
/*
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
*/
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;

constexpr ll MOD = (MOD_TYPE == 1 ? (ll)(1e9 + 7) : 998244353);
//constexpr ll MOD = 1;
constexpr int INF = (int)1e9 + 10;
constexpr ll LINF = (ll)4e18;
constexpr double PI = acos(-1.0);
constexpr double EPS = 1e-11;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};

#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define MP make_pair
#define MT make_tuple
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define possible(n) cout << ((n) ? "possible" : "impossible") << "\n"
#define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n"
#define Yay(n) cout << ((n) ? "Yay!" : ":(") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";

inline void init_main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(30) << setiosflags(ios::fixed);
}
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;
}
inline ll CEIL(ll a, ll b)
{
  return (a + b - 1) / b;
}
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val)
{
  fill((T *)array, (T *)(array + N), val);
}
template <typename T, typename U>
constexpr istream &operator>>(istream &is, pair<T, U> &p) noexcept
{
  is >> p.first >> p.second;
  return is;
}
template <typename T, typename U>
constexpr ostream &operator<<(ostream &os, pair<T, U> &p) noexcept
{
  os << p.first << " " << p.second;
  return os;
}
#pragma endregion

vector<pii> E[1000010];

void solve()
{
  int h, w;
  cin >> h >> w;
  int sh, sw, gh, gw;
  cin >> sh >> sw >> gh >> gw;
  sh--, sw--, gh--, gw--;
  vector<string> s(h);
  rep(i, h)
  {
    cin >> s[i];
  }

  rep(i, h) rep(j, w)
  {
    if (i != h - 1 and s[i][j] == '.' and s[i + 1][j] == '.')
    {
      E[i * w + j].emplace_back(MP((i + 1) * w + j, 0));
      E[(i + 1) * w + j].emplace_back(MP(i * w + j, 0));
    }
    if (j != w - 1 and s[i][j] == '.' and s[i][j + 1] == '.')
    {
      E[i * w + j].emplace_back(MP(i * w + j + 1, 0));
      E[i * w + j + 1].emplace_back(MP(i * w + j, 0));
    }
  }

  rep(i, h) rep(j, w)
  {
    if (s[i][j] == '#')
      continue;
    for (int ii = i - 2; ii <= i + 2; ii++)
    {
      for (int jj = j - 2; jj <= j + 2; jj++)
      {
        if (ii < 0 or ii >= h or jj < 0 or jj >= w or s[ii][jj] == '#')
          continue;
        E[i * w + j].emplace_back(MP(ii * w + jj, 1));
      }
    }
  }

  deque<int> que;
  que.push_front(sh * w + sw);
  int d[1000010];
  fill(d, d + 1000010, INF);
  d[sh * w + sw] = 0;
  while (!que.empty())
  {
    int q = que.front();
    que.pop_front();
    for (auto [to, cost] : E[q])
    {
      if (d[to] > d[q] + cost)
      {
        d[to] = d[q] + cost;
        if (cost == 0)
          que.push_front(to);
        else
          que.push_back(to);
      }
    }
  }
  cout << (d[gh * w + gw] == INF ? -1 : d[gh * w + gw]) << "\n";
}

int main()
{
  init_main();
  solve();
}


Measured memory_bytes: 123376