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

// エイリアス
using  ll = long signed long;
using ull = long unsigned long;
using  ld = long double;
using   P = pair<int, int>;
using llP = pair<ll, ll>;
using DoP = pair<double, double>;

// 汎用マクロ
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define FOREACH(i,q) for (auto &i : q)
#define UNIQUE(v) do { sort((v).begin(), (v).end()); (v).erase(unique((v).begin(), (v).end()), (v).end()); } while (false)
#define SZ(x) ((int)(x).size())
template <class T>inline bool chmin(T &a, const T b) {if (a > b) { a = b; return true;} return false;}
template <class T>inline bool chmax(T &a, const T b) {if (a < b) { a = b; return true;} return false;}
template <class T>inline void line_out(const vector<T> vec) {int n = SZ(vec); rep(i, n) { cout << vec[i]; if(i < n-1) cout << " ";}cout << endl;}
const int di[] = {0, 1, 0, -1, 1, 1, -1, -1};
const int dj[] = {1, 0, -1, 0, 1, -1, 1, -1};
const int di2[] = {1, 1, -1, -1, 0, 1, 2, 2, 2, 2, 2, 1, 0, -1, -2, -2, -2, -2, -2, -1};
const int dj2[] = {1, -1, 1, -1, 2, 2, 2, 1, 0, -1, -2, -2, -2, -2, -2, -1, 0, 1, 2, 2};
const int INF = 1 << 28;
const ll INF64 = 1ll << 55;
const int mod = 1000000007;
//const int mod = 998244353;
struct mint
{
  ll x; // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a)
  {
    if ((x += a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator-=(const mint a)
  {
    if ((x += mod - a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator*=(const mint a)
  {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const
  {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const
  {
    mint res(*this);
    return res -= a;
  }
  mint &operator++()
  {
    if ((x += 1) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator--()
  {
    if ((x += mod - 1) >= mod)
      x -= mod;
    return *this;
  }
  mint operator*(const mint a) const
  {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const
  {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
 
  // for prime mod
  mint inv() const
  {
    return pow(mod - 2);
  }
  mint &operator/=(const mint a)
  {
    return (*this) *= a.inv();
  }
  mint operator/(const mint a) const
  {
    mint res(*this);
    return res /= a;
  }
};



int main()
{
  int h, w; cin >> h >> w;
  int ch, cw, dh, dw;
  cin >> ch >> cw >> dh >> dw;
  --ch; --cw; --dh; --dw;
  vector<string> s(h);
  rep(i, h) cin >> s[i];

  deque<P> d;
  vector<vector<int>> dist(h, vector<int>(w, INF));

  auto update = [&](P now) {
    int i = now.first, j = now.second;
    rep(k, 4) {
      int ni = i+di[k], nj = j+dj[k];
      if(ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
      if(s[ni][nj] == '#') continue;

      if(chmin(dist[ni][nj], dist[i][j])) {
        d.push_front(P(ni, nj));
      }
    }

    rep(k, 20) {
      int ni = i+di2[k], nj = j+dj2[k];
      if(ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
      if(s[ni][nj] == '#') continue;

      if(chmin(dist[ni][nj], dist[i][j]+1)) {
        d.push_back(P(ni, nj));
      }
    }
  };

  d.push_back(P(ch, cw));
  dist[ch][cw] = 0;

  while(!d.empty()) {
    P now = d.front(); d.pop_front();
    update(now);
  }

  if(dist[dh][dw] != INF) cout << dist[dh][dw] << endl;
  else cout << -1 << endl;
}

Measured memory_bytes: 9564