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

constexpr int inf = 1001001001;
constexpr int dy[] = {-1, 0, 1, 0};
constexpr int dx[] = {0, 1, 0, -1};
using Graph = vector< vector< int > >;

int main() {
  int h, w;
  cin >> h >> w;

  auto to_v = [w](int y, int x) {
    return y * w + x;
  };

  auto from_v = [w](int v, int &y, int &x) {
    y = v / w;
    x = v % w;
  };

  int Ya, Xa, Yb, Xb;
  cin >> Ya >> Xa >> Yb >> Xb;

  Ya -= 1; Xa -= 1;
  Yb -= 1; Xb -= 1;

  int a = to_v(Ya, Xa);
  int b = to_v(Yb, Xb);

  vector< string > ss(h);
  for (auto &s : ss) cin >> s;
  ss[Ya][Xa] = 'A';
  ss[Yb][Xb] = 'B';

  int V = to_v(h, w);

  auto make_graph = [&](const vector< string > &ss) {
    Graph G(V);
    for (int y = 1; y + 1 < h; y++) {
      for (int x = 1; x + 1 < w; x++) {
        if (ss[y][x] == '#') continue;

        int v = to_v(y, x);
        for (int i = 0; i < 4; i++) {
          int ny = y + dy[i];
          int nx = x + dx[i];
          if (ss[ny][nx] == '#') continue;

          int u = to_v(ny, nx);
          G[v].emplace_back(u);
        }
      }
    }

    return G;
  };

  vector< int > pre(V, -1);

  auto bfs = [&](int s, const Graph &G) {
    int n = G.size();
    vector< pair< int, int > > d(n, {inf, 0});

    queue< int > que;
    
    que.push(s);
    d[s] = make_pair(0, 1);

    while (not que.empty()) {
      int v = que.front();
      que.pop();

      for (auto &u : G[v]) {
        if (d[u].first < d[v].first + 1) continue;
        if (d[u].first == d[v].first + 1) {
          d[u].second = 2;
          continue;
        }

        d[u] = d[v];
        d[u].first += 1;
        que.push(u);
        pre[u] = v;
      }
    }

    return d;
  };

  auto G = make_graph(ss);
  auto bs = bfs(b, G);
  auto as = bfs(a, G);

  int ans = inf;
  if (as[b].second == 0) {
    ans = -1;
  }

  if (as[b].second >= 2) {
    ans = 2 * as[b].first;
  }

  if (as[b].second != 0) {
    int v = pre[b];
    while (v != a) {
      int y, x;
      from_v(v, y, x);
      ss[y][x] = 'x';
      v = pre[v];
    }
  }

  for (int y = 1; y + 1 < h; y++) {
    for (int x = 1; x + 1 < w; x++) {
      if (ss[y][x] != 'x') continue;
      for (int i = 0; i < 4; i++) {
        int ny = y + dy[i];
        int nx = x + dx[i];
        if (ss[ny][nx] == '.') {
          ans = min(ans, 2 * as[b].first + 2);
        }
      }
    }
  }

  for (int v = 0; v < V; v++) {
    if (as[v].second == 0) continue;
    if ((int)G[v].size() < 3) continue;
    int cost = 2 * (as[v].first + bs[v].first) + 4;
    ans = min(ans, cost);
  }

  {
    for (int y = 1; y + 1 < h; y++) {
      for (int x = 1; x + 1 < w; x++) {
        if (ss[y][x] != 'x') continue;
        ss[y][x] = '#';
      }
    }

    ss[Yb][Xb] = '#';

    G = make_graph(ss);
    auto nas = bfs(a, G);

    for (int i = 0; i < 4; i++) {
      int y = Yb + dy[i];
      int x = Xb + dx[i];
      int v = to_v(y, x);
      if (v == a) continue;
      if (nas[v].second == 0) continue;
      ans = min(ans, as[b].first + nas[v].first + 1);
    }
  }

  if (ans == inf) ans = -1;
  cout << ans << endl;
}