#include <bits/stdc++.h>

using namespace std;

using pi = pair< int, int >;
constexpr int inf = 1 << 30;
constexpr int vy[] = {-1, 1, 0, 0};
constexpr int vx[] = {0, 0, -1, 1};

template< typename T, typename E >
bool chmin(T &a, E b) {
  if(a > b) {
    a = b;
    return true;
  } else {
    return false;
  }
}

int main() {
  int H, W, Ya, Xa, Yb, Xb;
  cin >> H >> W >> Ya >> Xa >> Yb >> Xb;
  --Ya, --Xa, --Yb, --Xb;
  vector< string > S(H);
  for(auto &s : S) cin >> s;

  vector< vector< int > > min_cost(H, vector< int >(W, inf));
  vector< vector< int > > ways(H, vector< int >(W, 0));
  vector< vector< int > > from(H, vector< int >(W, -1));

  {
    queue< pi > que;
    min_cost[Ya][Xa] = 0;
    ways[Ya][Xa] = 1;
    que.emplace(Ya, Xa);
    while(!que.empty()) {
      auto[y, x] = que.front();
      que.pop();
      for(int k = 0; k < 4; k++) {
        int ny = y + vy[k];
        int nx = x + vx[k];
        if(S[ny][nx] == '#') continue;
        if(chmin(min_cost[ny][nx], min_cost[y][x] + 1)) {
          from[ny][nx] = k;
          ways[ny][nx] = 0;
          que.emplace(ny, nx);
        }
        if(min_cost[y][x] + 1 == min_cost[ny][nx]) {
          ways[ny][nx] += ways[y][x];
          chmin(ways[ny][nx], 2);
        }
      }
    }
  }

  if(ways[Yb][Xb] == 0) {
    cout << -1 << "\n";
    return 0;
  }

  if(ways[Yb][Xb] >= 2) {
    cout << min_cost[Yb][Xb] * 2 << "\n";
    return 0;
  }

  vector< pair< int, int > > path;
  int cy = Yb, cx = Xb;
  path.emplace_back(cy, cx);
  while(cy != Ya || cx != Xa) {
    int py = cy + vy[from[cy][cx] ^ 1];
    int px = cx + vx[from[cy][cx] ^ 1];
    cy = py;
    cx = px;
    path.emplace_back(cy, cx);
  }

  assert(min_cost[Yb][Xb] + 1 == path.size());

  for(auto &p : path) S[p.first][p.second] = '*';

  for(int i = 1; i + 1 < path.size(); i++) {
    for(int j = 0; j < 4; j++) {
      int ny = path[i].first + vy[j];
      int nx = path[i].second + vx[j];
      if(S[ny][nx] == '.') {
        cout << min_cost[Yb][Xb] * 2 + 2 << "\n";
        return 0;
      }
    }
  }


  int ret = inf;

  {
    vector< vector< int > > min_cost2(H, vector< int >(W, inf));
    queue< pi > que;
    min_cost2[Ya][Xa] = 0;
    que.emplace(Ya, Xa);
    while(!que.empty()) {
      auto[y, x] = que.front();
      que.pop();
      for(int k = 0; k < 4; k++) {
        int ny = y + vy[k];
        int nx = x + vx[k];
        if(S[ny][nx] == '#' || S[ny][nx] == '*') continue;
        if(chmin(min_cost2[ny][nx], min_cost2[y][x] + 1)) {
          que.emplace(ny, nx);
        }
      }
    }
    if(min_cost2[Yb][Xb] != inf) {
      chmin(ret, min_cost2[Yb][Xb] + min_cost[Ya][Xa]);
    }
  }


  cout << ret << "\n";

}