#define LOCAL
#define _USE_MATH_DEFINES
#include <array>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>
#include <complex>
#include <cmath>
#include <numeric>
#include <bitset>
#include <functional>
#include <random>
#include <ctime>

using namespace std;

template <typename A, typename B>
ostream& operator <<(ostream& out, const pair<A, B>& a) {
  out << "(" << a.first << "," << a.second << ")";
  return out;
}
template <typename T, size_t N>
ostream& operator <<(ostream& out, const array<T, N>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T>
ostream& operator <<(ostream& out, const vector<T>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T, class Cmp>
ostream& operator <<(ostream& out, const set<T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
  return out;
}
template <typename U, typename T, class Cmp>
ostream& operator <<(ostream& out, const map<U, T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& p : a) { out << (first ? "" : ", "); out << p.first << ":" << p.second; first = 0;} out << "}";
  return out;
}
#ifdef LOCAL
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
#else
#define trace(...) 42
#endif
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
  cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << ": " << arg1 << " |";
  __f(comma + 1, args...);
}

typedef long long int64;
typedef pair<int, int> ii;
#define SZ(x) (int)((x).size())
const int INF = 1 << 29;
const int MOD = 1e9 + 7;
mt19937 mrand(random_device{}());
int rnd(int x) { return mrand() % x; }

struct fast_ios {
  fast_ios() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
  };
} fast_ios_;

const int dir[4][2] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};

int main() {
  int n, m;
  cin >> n >> m;
  int sx, sy, tx, ty;
  cin >> sx >> sy >> tx >> ty;
  --sx; --sy; --tx; --ty;
  vector<string> s(n);
  for (int i = 0; i < n; ++i) cin >> s[i];
  vector<int> d(n * m, INF);
  priority_queue<ii, vector<ii>, greater<ii>> Q;
  int u = sx * m + sy;
  d[u] = 0;
  Q.push({d[u], u});
  while (!Q.empty()) {
    auto [dd, u] = Q.top();
    Q.pop();
    if (dd != d[u]) continue;
    int x = u / m, y = u % m;
    for (int k = 0; k < 4; ++k) {
      int nx = x + dir[k][0];
      int ny = y + dir[k][1];
      if (nx < 0 || nx >= n || ny < 0 || ny >= m) continue;
      if (s[nx][ny] == '#') continue;
      int v = nx * m + ny;
      if (d[v] > d[u]) {
        d[v] = d[u];
        Q.push({d[v], v});
      }
    }
    for (int i = -2; i <= 2; ++i) {
      for (int j = -2; j <= 2; ++j) {
        int nx = x + i;
        int ny = y + j;
        if (nx < 0 || nx >= n || ny < 0 || ny >= m) continue;
        if (s[nx][ny] == '#') continue;
        int v = nx * m + ny;
        if (d[v] > d[u] + 1) {
          d[v] = d[u] + 1;
          Q.push({d[v], v});
        }
      }
    }
  }
  int ret = d[tx * m + ty];
  if (ret == INF) ret = -1;
  cout << ret << endl;
  return 0;
}


Measured memory_bytes: 8600