#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

constexpr int INF = 1001001001;
template <int k = 2, class T>  // cost in [0, k)
int kBFS(const vector<vector<pair<int, T>>>& g, int s, int goal) {
  static_assert(k >= 1);
  const int n = g.size();
  vector<int> dist(n, INF);
  vector<int> q[2 * k];
  dist[s] = 0;
  q[0].emplace_back(s);
  for (int dist_cur = 0, ptr = 0;;) {
    const auto qb = q + ptr;
    while (!qb[0].empty()) {
      int u = qb[0].back();
      qb[0].pop_back();
      if (dist[u] != dist_cur) continue;
      if (u == goal) return dist_cur;
      for (auto [v, c] : g[u]) {
        int nd = dist_cur + c;
        if (nd < dist[v]) {
          dist[v] = nd;
          qb[c].emplace_back(v);
        }
      }
    }
    do {
      dist_cur++;
      ptr++;
      if (ptr == 2 * k) return -1;
    } while (q[ptr].empty());
    if (ptr > k) {
      for (int i = ptr; i < 2 * k; i++) {
        swap(q[i], q[i - ptr]);
      }
      ptr = 0;
    }
  }
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w;
  cin >> h >> w;
  int sx, sy, gx, gy;
  cin >> sx >> sy >> gx >> gy;
  sx--, sy--, gx--, gy--;
  char s[2010][2010];
  rep(i, h) cin >> s[i];
  vector<vector<pair<int, bool>>> to(h * w * 2);
  const int tot = h * w;
  rep(i, h - 1) rep(j, w) {
    int v = tot + i * w + j;
    to[v + w].emplace_back(v, 0);
  }
  rep(i, h) rep(j, w) if (s[i][j] == '.') {
    int v = i * w + j;
    to[tot + v].emplace_back(v, 0);
  }
  short i_last[2000][2000];
  rep(j, w) {
    int il = 0;
    rep(i, h) {
      if (s[i][j] == '.') il = i;
      i_last[i][j] = il;
    }
  }
  rep(i, h) rep(j, w) if (s[i][j] == '.') {
    for(int dj: {1, -1}) {
      int nj = j + dj;
      if (!(0 <= nj && nj < w)) continue;
      to[i*w + j].emplace_back(tot + min(h-1, i+1)*w + nj, 0);
      int il = i_last[min(h-1, i+1)][nj];
      nj += dj;
      if (0 <= nj && nj < w) {
        int e = max(0, i - il);
        to[i*w + j].emplace_back(tot + min(h-1, il + 1 + e / 2)*w + nj, 0);
        to[i*w + j].emplace_back(tot + min(h-1, i+1)*w + nj, 1);
      }
    }
    if (w != 1) {
      to[i*w + j].emplace_back(tot + min(h-1, i+1)*w + j, 1);
    }
  }
  int ans = kBFS(to, sx*w + sy, gx * w + gy);
  cout << ans << '\n';
}