#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <limits>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define eprintf(...) 42
#endif
using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vvvll = std::vector<vvll>;
#define reps(i, S, E) for (ll i = (S); i <= (E); i++)
#define rep(i, N) reps(i, 0, N-1)
#define deps(i, E, S) for (ll i = (E); i >= (S); i--)
#define dep(i, N) deps(i, N-1, 0)
const ll INF = 1LL << 60;
const int INF_INT = 1 << 30;

template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
#define CEIL(x, y) ((x + y - 1) / (y))
struct mll {
	static ll MOD;
	ll val;
	mll(ll v = 0) : val(v % MOD) { if (val < 0) val += MOD; }
	mll operator - () const { return -val; }
	mll operator + (const mll &b) const { return val + b.val; }
	mll operator - (const mll &b) const { return val - b.val; }
	mll operator * (const mll &b) const { return val * b.val; }
	mll operator / (const mll &b) const { return mll(*this) /= b; }
	mll operator + (ll b) const { return *this + mll(b); }
	mll operator - (ll b) const { return *this - mll(b); }
	mll operator * (ll b) const { return *this * mll(b); }
	friend mll operator + (ll a, const mll &b) { return b + a; }
	friend mll operator - (ll a, const mll &b) { return -b + a; }
	friend mll operator * (ll a, const mll &b) { return b * a; }
	mll &operator += (const mll &b) { val = (val + b.val) % MOD; return *this; }
	mll &operator -= (const mll &b) { val = (val + MOD - b.val) % MOD; return *this; }
	mll &operator *= (const mll &b) { val = (val*b.val) % MOD; return *this; }
	mll &operator /= (const mll &b) {
		ll c = b.val, d = MOD, u = 1, v = 0;
		while (d) {
			ll t = c / d;
			c -= t * d; swap(c, d);
			u -= t * v; swap(u, v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll &operator += (ll b) { return *this += mll(b); }
	mll &operator -= (ll b) { return *this -= mll(b); }
	mll &operator *= (ll b) { return *this *= mll(b); }
	mll &operator /= (ll b) { return *this /= mll(b); }
	bool operator == (const mll &b) { return val == b.val; }
	bool operator != (const mll &b) { return val != b.val; }
	bool operator == (ll b) { return *this == mll(b); }
	bool operator != (ll b) { return *this != mll(b); }
	friend bool operator == (ll a, const mll &b) { return mll(a) == b.val; }
	friend bool operator != (ll a, const mll &b) { return mll(a) != b.val; }
	friend ostream &operator << (ostream &os, const mll &a) { return os << a.val; }
	friend istream &operator >> (istream &is, mll &a) { return is >> a.val; }
	static mll Combination(ll a, ll b) {
		chmin(b, a - b);
		if (b < 0) return mll(0);
		mll c = 1;
		rep(i, b) c *= a - i;
		rep(i, b) c /= i + 1;
		return c;
	}
};
using vmll = std::vector<mll>;
using vvmll = std::vector<vmll>;
using vvvmll = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;

struct Fast {
	Fast() {
		cin.tie(0);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(std::numeric_limits<double>::max_digits10);
	}
} fast; //cin,cout高速化のおまじない＋桁数指定

ll mll::MOD = (ll)(1e9 + 7);// 998244353ll;

//--for debug--
#ifdef LOCAL
void _debug_out_(string s = "") {
	if (s != "") { eprintf(s.c_str()); }
	else { eprintf("\n"); }
}
void _debug_out_(ll x, string s = "") {
	if (s != "") { eprintf(s.c_str(), x); }
	else { eprintf("%lld\n", x); }
}
void _debug_out_(mll x, string s = "") {
	if (s != "") { eprintf(s.c_str(), x); }
	else { eprintf("%lld\n", x.val); }
}
void _debug_out_(vvll x, string s = "") {
	string t = s;
	if (s == "") {
		ll maxLen = 0;
		rep(i, (ll)x.size()) rep(j, (ll)x[i].size()) {
			ll n = x[i][j] / 10, len = 1;
			while (n > 0) { len++; n /= 10; }
			chmax(maxLen, len);
		}
		t = "%" + to_string(maxLen) + "lld ";
	}
	rep(i, (ll)x.size()) { rep(j, (ll)x[i].size()) { eprintf(t.c_str(), x[i][j]); } eprintf("\n"); }
	eprintf("\n");
}
void _debug_out_(vll x, string s = "") {
	rep(i, (ll)x.size()) { if (s != "") { eprintf(s.c_str(), x[i]); } else { eprintf("%lld ", x[i]); } }
	eprintf("\n");
}
void _debug_out_(vector<bool> x) {
	rep(i, (ll)x.size()) { eprintf("%s", x[i] ? "o" : "x"); }
	eprintf("\n");
}
void _debug_out_(vector<vector<bool>> x) {
	rep(i, (ll)x.size()) { rep(j, (ll)x[i].size()) { eprintf("%s", x[i][j] ? "o" : "x"); } eprintf("\n"); }
	eprintf("\n");
}
void _debug_out_(map<ll, ll> x) {
	auto begin = x.begin(), end = x.end();
	for (auto iter = begin; iter != end; iter++) { eprintf("%lld:%lld ", iter->first, iter->second); }
	eprintf("\n");
}
void _debug_out_(map<char, ll> x) {
	auto begin = x.begin(), end = x.end();
	for (auto iter = begin; iter != end; iter++) { eprintf("%c:%lld ", iter->first, iter->second); }
	eprintf("\n");
}
#define debug_out(...) _debug_out_(__VA_ARGS__)
#else
#define debug_out(...) 42
#endif
//!--for debug--


//◆--↓--グラフテンプレート--↓--
template<typename T>
struct edge {
	ll src, to;
	T cost;
	edge(ll to, T cost) : src(-1), to(to), cost(cost) {}
	edge(ll src, ll to, T cost) : src(src), to(to), cost(cost) {}
	edge &operator=(const ll &x) {
		to = x;
		return *this;
	}
	operator ll() const { return to; }
};
template<typename T>
using Edges = vector<edge<T>>;
template<typename T>
using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<ll>>;
template<typename T>
using Matrix = vector<vector<T>>;
//--↑--グラフテンプレート--↑--



//◆--↓--ダイクストラ：O(E * logV)--↓--
template<typename T>
vector<T> dijkstra(WeightedGraph<T> &g, ll s) {
	//const auto INF = numeric_limits<T>::max();
	vector<T> dist(g.size(), INF);

	using Pi = pair<T, ll>;
	priority_queue<Pi, vector<Pi>, greater<Pi>> que;
	dist[s] = 0;
	que.emplace(dist[s], s);
	while (!que.empty()) {
		T cost;
		ll idx;
		tie(cost, idx) = que.top();
		que.pop();
		if (dist[idx] < cost) continue;
		for (auto &e : g[idx]) {
			auto next_cost = cost + e.cost;
			if (dist[e.to] <= next_cost) continue;
			dist[e.to] = next_cost;
			que.emplace(dist[e.to], e.to);
		}
	}
	return dist;
}
//usage
//int V, E, R;
//scanf("%d %d %d", &V, &E, &R);
//WeightedGraph<ll> g(V);
//for (int i = 0; i < E; i++) {
//	int a, b, c;
//	scanf("%d %d %d", &a, &b, &c);
//	g[a].emplace_back(b, c);
//}
//vector<int> distance = dijkstra(g, R); //R:start point
//--↑--ダイクストラ--↑--



void solve() {
	ll H;
	cin >> H;
	ll W;
	cin >> W;
	ll Ch;
	cin >> Ch;
	ll Cw;
	cin >> Cw;
	ll Dh;
	cin >> Dh;
	ll Dw;
	cin >> Dw;
	Ch--;
	Cw--;
	Dh--;
	Dw--;
	vector<string> S(H);
	rep(i, H) {
		cin >> S[i];
	}

	vvll l(H, vll(W, -1));
	queue<pair<ll, ll>> q;
	ll num_label = 0;
	ll dy[] = { 0, 1, 0, -1 };
	ll dx[] = { 1, 0, -1, 0 };

	rep(i, H) rep(j, W) {
		if (l[i][j] >= 0) {
			continue;
		}
		if (S[i][j] == '#') {
			continue;
		}

		l[i][j] = num_label;
		num_label++;
		q.emplace(i, j);
		while (q.empty() == false) {
			auto curr = q.front();
			q.pop();

			//4方向を探索
			rep(dir, 4) {
				ll toY = curr.first + dy[dir];
				ll toX = curr.second + dx[dir];

				//範囲外
				if (toY < 0 || toY >= H || toX < 0 || toX >= W) {
					continue;
				}

				//通れない場所
				if (S[toY][toX] == '#') {
					continue;
				}

				//既に探索済み
				if (l[toY][toX] >= 0) {
					continue;
				}

				//キューに入れて探索継続
				l[toY][toX] = l[curr.first][curr.second];
				q.emplace(toY, toX);
			}
		}
	}

	//debug_out(l);


	//WeightedGraph<ll> g(V);
	//for (int i = 0; i < E; i++) {
	//	int a, b, c;
	//	scanf("%d %d %d", &a, &b, &c);
	//	g[a].emplace_back(b, c);
	//}
	//vector<int> distance = dijkstra(g, R); //R:start point

	WeightedGraph<ll> g(num_label);
	rep(i, H) rep(j, W) {
		if (l[i][j] < 0) {
			continue;
		}

		ll label = l[i][j];

		ll left = max(0ll, j - 2);
		ll right = min(W - 1, j + 2);
		ll top = max(0ll, i - 2);
		ll bottom = min(H - 1, i + 2);

		reps(h, top, bottom) reps(w, left, right) {
			ll toLabel = l[h][w];
			if (toLabel == label || toLabel < 0) {
				continue;
			}

			bool found = false;
			rep(k, (ll)g[label].size()) {
				if (g[label][k].to == toLabel) {
					found = true;
					break;
				}
			}

			if (!found) {
				g[label].emplace_back(toLabel, 1);
			}
		}
	}

	vll distance = dijkstra(g, l[Ch][Cw]); //R:start point

	ll result = distance[l[Dh][Dw]];

	if (result == INF) {
		cout << -1 << endl;
	}
	else {
		cout << result << endl;
	}

}

int main() {
#if TEST && LOCAL
	ll t; cin >> t;
	rep(i, t) { solve(); }
#else
	solve();
#endif
	return 0;
}


Measured memory_bytes: 28968