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

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

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

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

  int a = to_v(Ya - 1, Xa - 1);
  int b = to_v(Yb - 1, Xb - 1);

  vector< string > ss(h);
  for (auto &s : ss) cin >> s;

  int V = h * w;
  vector< vector< int > > G(V);

  constexpr int dy[] = {-1, 0, 1, 0};
  constexpr int dx[] = {0, 1, 0, -1};
  for (int y = 1; y < h - 1; y++) {
    for (int x = 1; x < w - 1; 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);
      }
    }
  }

  constexpr int inf = 1001001001;
  auto bfs = [&](int s) {
    vector< vector< int > > res(V);
    res[s].emplace_back(0);

    struct t {
      int v, pre, cost;
      t(int v_, int pre_, int cost_) : v(v_), pre(pre_), cost(cost_) {}
    };

    queue< t > que;
    que.emplace(s, -1, 0);

    while (not que.empty()) {
      auto [v, pre, cost] = que.front();
      que.pop();

      for (auto &u : G[v]) {
        if (u == pre) continue;
        if ((int)res[u].size() == 2) continue;
        res[u].emplace_back(cost + 1);
        que.emplace(u, v, cost + 1);
      }
    }

    return res;
  };

  auto da = bfs(a);
  auto db = bfs(b);

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

  if ((int)da[b].size() == 2) {
    ans = min(ans, da[b][0] + db[a][1]);
  }

  auto find_fromv = [&](int y, int x, const vector< vector< int > > &dist) {
    int f = to_v(y, x);
    for (int i = 0; i < 4; i++) {
      int u = to_v(y + dy[i], x + dx[i]);
      if ((int)dist[u].size() == 0) continue;
      if (dist[u][0] > dist[f][0]) continue;
      f = u;
    }
    return f;
  };

  for (int y = 1; y < h - 1; y++) {
    for (int x = 1; x < w - 1; x++) {
      int v = to_v(y, x);
      if ((int)da[v].size() == 0) continue;
      if ((int)db[v].size() == 0) continue;
      if ((int)G[v].size() < 3) continue;

      int af = find_fromv(y, x, da);
      int bf = find_fromv(y, x, db);

      int cost = 2 * (da[v][0] + db[v][0]);
      if (af == bf or af == v or bf == v) {
        cost += 4;
      } else {
        cost += 2;
      }

      ans = min(ans, cost);
    }
  }

  if (ans == inf) {
    ans = -1;
  }

  cout << ans << endl;
}