#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;
  vector< int > rs(V);
  auto bfs = [&](int s) {
    queue< int > que;
    que.emplace(s);

    vector< int > res(V, inf);
    res[s] = 0;

    rs.assign(V, 0);
    rs[s] = 1;

    while (not que.empty()) {
      int v = que.front();
      que.pop();
      for (auto &u : G[v]) {
        if (res[u] == res[v] + 1) {
          rs[u] = 2;
        }
        if (res[u] > res[v] + 1) {
          res[u] = res[v] + 1;
          rs[u] = rs[v];
          que.emplace(u);
        }
      }
    }

    return res;
  };

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

  int ans = inf;
  if (rs[a] == 0) {
    ans = -1;
  }
  if (rs[a] >= 2) {
    ans = da[b] + db[a];
  }
  for (int y = 1; y < h - 1; y++) {
    for (int x = 1; x < w - 1; x++) {
      int v = to_v(y, x);
      if (rs[v] == 0) continue;
      if ((int)G[v].size() < 3) continue;

      int af = v;
      for (int i = 0; i < 4; i++) {
        int u = to_v(y + dy[i], x + dx[i]);
        if (da[u] > da[af]) continue;
        af = u;
      }
      
      int bf = v;
      for (int i = 0; i < 4; i++) {
        int u = to_v(y + dy[i], x + dx[i]);
        if (db[u] > db[bf]) continue;
        bf = u;
      }

      if (af == bf or af == v or bf == v) {
        ans = min(ans, 2 * (da[v] + db[v]) + 4);
      } else {
        ans = min(ans, 2 * (da[v] + db[v]) + 2);
      }
    }
  }

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

  cout << ans << endl;
}