#include <bits/stdc++.h>
	
using namespace std;
 
#define int long long
 
#define PB	push_back
#define ALL(x)	(x).begin(), (x).end()
#define ALLR(x)	(x).rbegin(), (x).rend()
#define MP	make_pair
 
template <typename A, typename B>
string to_string(pair<A, B> p);
 
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
 
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
 
string to_string(const string& s) {
  return '"' + s + '"';
}
 
string to_string(const char* s) {
  return to_string((string) s);
}
 
string to_string(bool b) {
  return (b ? "true" : "false");
}
 
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
 
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
 
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
 
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
 
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}
 
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
 
void debug_out() { cerr << endl; }
 
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#define LOCAL
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
 
#define FAST_IO ios::sync_with_stdio(false); cin.tie(0)
 
typedef pair<int, int> ii;
typedef pair<pair<int, int>, int> iii;
typedef vector<int> vi;
typedef vector<iii> viii;
typedef vector<vi> vvi;
typedef vector<ii> vii;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef unsigned long long ull;
 
const int INF = LONG_LONG_MAX;
const int NINF = LONG_LONG_MIN/2;
const double PI = 3.141592653589793238;

//MODULAR ARITHMATIC
const int mmod = 1000000000+7 ;

int add(int a, int b, int m=mmod) {
	return (a%m + b%m)%m;
}

int sub(int a, int b, int m=mmod) {
    return (a%m - b%m + m)%m;
}

int mul(int a, int b, int m=mmod) {
	return ((a%m) * (b%m) % m);
}

int pwr(int a, int b, int m=mmod) {
    a %= m;
    int r = 1;
    while (b) {
		if (b&1) r = r*a%m;
		b >>= 1;
		a = a*a%m;
    }
    return r;
}

int inv(int a, int m=mmod) {
	return pwr(a, m-2, m);
}

bool multi = false;
struct Solve {
	string endl = "\n";
	
	Solve() {
		int h, w;
		cin >> h >> w;
		int ch, cw;
		cin >> ch >> cw;
		int dh, dw;
		cin >> dh >> dw;
		
		string s[h];
		for (int i = 0; i < h; i++) {
			cin >> s[i];
		}
		
		vector<vector<bool>> vis(h+1, vb(w+1, false));
		
		queue<ii> q;
		int cnt = 0;
		q.push({ch, cw});
		
		bool ok = true;
		vector<ii> list;
		while (true) {
			for (int i = 0; i < (int)list.size(); i++) {
				for (int j = -2; j <= 2; j++) {
					for (int k = -2; k <= 2; k++) {
						if (list[i].first + j >= 1 && list[i].second + k >= 1 &&
						    list[i].first + j <= h && list[i].second + k <= w) {
							if (s[list[i].first+j-1][list[i].second+k-1] == '.' && !vis[list[i].first+j][list[i].second+k]) {
								vis[list[i].first+j][list[i].second+k] = true;
								q.push({list[i].first+j, list[i].second+k});
							}
						}
					}
				}
			}
						
			if ((int)q.size() == 0) {
				ok = false;
				break;
			}

			list.clear();
			while (!q.empty()) {
				ii cur = q.front();
				//~ debug(cur);
				q.pop();
				//~ debug(cur);
				list.PB(cur);
				//~ cout << vis[cur.first][cur.second] << endl;
				
				vis[cur.first][cur.second] = true;
				if (cur.first + 1 <= h && s[cur.first][cur.second-1] == '.' && vis[cur.first+1][cur.second] == false) {
					q.push({cur.first+1, cur.second});
					vis[cur.first+1][cur.second] = true;
				}
				if (cur.first - 1 >= 1 && s[cur.first-2][cur.second-1] == '.' && vis[cur.first-1][cur.second] == false) {
					q.push({cur.first-1, cur.second});
					vis[cur.first-1][cur.second] = true;		
				}
				if (cur.second + 1 <= w && s[cur.first-1][cur.second] == '.' && vis[cur.first][cur.second+1] == false) {
					q.push({cur.first, cur.second+1});
					vis[cur.first][cur.second+1] = true;
				}
				if (cur.second - 1 >= 1 && s[cur.first-1][cur.second-2] == '.' && vis[cur.first][cur.second-1] == false) {
					q.push({cur.first, cur.second-1});
					vis[cur.first][cur.second-1] = true;
				}
				//~ debug(list);
				//~ debug(q.size());
			}
			
			if ((int)list.size() == 0) {
				ok = false;
				break;
			}
			if (vis[dh][dw]) {
				break;
			}
			cnt++;
		}
		
		if (ok) {
			cout << cnt << endl;
		} else {
			cout << -1 << endl;
		}
		
	}
};

int32_t main() {
	FAST_IO;
	
	int T=1;
	if (multi)
		cin >> T;
	for (int i = 1; i <= T; i++) {
		Solve me;
	}
}
// g++ -Wall -Wextra -pedantic -std=c++17 -O2 -Wshadow -Wformat=2 -Wfloat-equal -Wconversion -Wlogical-op -Wshift-overflow=2 -Wduplicated-cond -Wcast-qual -Wcast-align -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC -D_FORTIFY_SOURCE=2 -fsanitize=address -fsanitize=undefined -fno-sanitize-recover -fstack-protector


Measured memory_bytes: 4968