#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int h, w, ra, ca, rb, cb; cin >> h >> w >> ra >> ca >> rb >> cb; --ra; --ca; --rb; --cb;
  vector<string> s(h); REP(i, h) cin >> s[i];
  vector dist(h, vector(w, -1)), dp(h, vector(w, 0));
  dist[ra][ca] = 0;
  dp[ra][ca] = 1;
  vector prev(h, vector(w, make_pair(-1, -1)));
  queue<pair<int, int>> que({{ra, ca}});
  while (!que.empty()) {
    auto [i, j] = que.front(); que.pop();
    REP(k, 4) {
      int y = i + dy[k], x = j + dx[k];
      if (s[y][x] == '.') {
        if (dist[y][x] == -1) {
          dist[y][x] = dist[i][j] + 1;
          dp[y][x] = dp[i][j];
          prev[y][x] = {i, j};
          que.emplace(y, x);
        } else if (dist[y][x] == dist[i][j] + 1) {
          dp[y][x] = min(dp[y][x] + dp[i][j], 2);
        }
      }
    }
  }
  if (dist[rb][cb] == -1) {
    cout << "-1\n";
    return 0;
  }
  if (dp[rb][cb] == 2) {
    cout << dist[rb][cb] * 2 << '\n';
    return 0;
  }
  s[rb][cb] = 'b';
  int cr = rb, cc = cb;
  while (cr != ra || cc != ca) {
    tie(cr, cc) = prev[cr][cc];
    s[cr][cc] = '$';
  }
  s[ra][ca] = 'a';
  REP(i, h) REP(j, w) {
    if (s[i][j] == '$') {
      REP(k, 4) {
        int y = i + dy[k], x = j + dx[k];
        if (s[y][x] == '.') {
          cout << dist[rb][cb] * 2 + 2 << '\n';
          return 0;
        }
      }
    }
  }
  s[ra][ca] = s[rb][cb] = '.';
  int ans = INF;
  {
    int cnt = 0;
    REP(k, 4) {
      int y = ra + dy[k], x = ca + dx[k];
      cnt += s[y][x] == '.';
    }
    if (cnt >= 3) chmin(ans, dist[rb][cb] * 2 + 4);
  }
  {
    int cnt = 0;
    REP(k, 4) {
      int y = rb + dy[k], x = cb + dx[k];
      cnt += s[y][x] == '.';
    }
    if (cnt >= 3) chmin(ans, dist[rb][cb] * 2 + 4);
  }
  s[rb][cb] = '$';
  vector dista(h, vector(w, -1));
  dista[ra][ca] = 0;
  que.emplace(ra, ca);
  while (!que.empty()) {
    auto [i, j] = que.front(); que.pop();
    int cnt = 0;
    REP(k, 4) {
      int y = i + dy[k], x = j + dx[k];
      if (s[y][x] == '.') {
        ++cnt;
        if (dista[y][x] == -1) {
          dista[y][x] = dista[i][j] + 1;
          que.emplace(y, x);
        }
      }
    }
    if (cnt >= 3) chmin(ans, dist[rb][cb] * 2 + (dista[i][j] + 1) * 4);
  }
  s[ra][ca] = '$';
  REP(k, 4) {
    int y = rb + dy[k], x = cb + dx[k];
    if (s[y][x] == '.' && dista[y][x] != -1) chmin(ans, dist[rb][cb] + dista[y][x] + 1);
  }
  s[rb][cb] = '.';
  vector distb(h, vector(w, -1));
  distb[rb][cb] = 0;
  que.emplace(rb, cb);
  while (!que.empty()) {
    auto [i, j] = que.front(); que.pop();
    int cnt = 0;
    REP(k, 4) {
      int y = i + dy[k], x = j + dx[k];
      if (s[y][x] == '.') {
        ++cnt;
        if (distb[y][x] == -1) {
          distb[y][x] = distb[i][j] + 1;
          que.emplace(y, x);
        }
      }
    }
    if (cnt >= 3) chmin(ans, dist[rb][cb] * 2 + (distb[i][j] + 1) * 4);
  }
  cout << (ans == INF ? -1 : ans) << '\n';
  return 0;
}