#include <iostream>
#include <vector>
#include <deque>
#include <algorithm>
#include <numeric>
#include <string>
#include <cstring>
#include <list>
#include <unordered_set>
#include <tuple>
#include <cmath>
#include <limits>
#include <type_traits>
#include <iomanip>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <set>
#include <bitset>
#include <complex>
#include <regex>
#include <random>
using namespace std;

#define rep(i,n)	for(lint i = 0; i < n; i++)
#define repr(i,n)	for(lint i = n - 1; i >= 0; i--)
#define repi(i,ini,n)	for(lint i = ini; i < n; i++)
#define repir(i,ini,n)	for(lint i = n-1; i >= ini; i--)
#define repb(i,start,end)	for(lint i = start; i <= end; i++)
#define repbr(i,start,end)	for(lint i = end; i >= start; i--)

#define bit(n)				(1LL << (n))

#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define rg(v, ini, end) v.begin() + ini, v.begin()+end

#define ret return 0;
#define chmax(a, b) a=max(a,b)
#define chmin(a, b) a=min(a,b)

using lint = long long;
using ulint = unsigned long long;
using ld = long double;
struct xy
{
	lint x, y;
	xy() :x(0), y(0) {}
	xy(lint _x, lint _y) : x(_x), y(_y) {}
	xy operator+(const xy& p) const
	{
		return xy(x + p.x, y + p.y);
	}
	bool operator<(xy p) const
	{
		if (y == p.y)
			return x < p.x;
		return y < p.y;
	}
};
struct xyd
{
	ld x, y;
	xyd() :x(0), y(0) {}
	xyd(long double _x, long double _y) : x(_x), y(_y) {}
};
using vec = vector<lint>;
using vecd = vector<ld>;
using vecs = vector<string>;
using vecp = vector<xy>;
template<class T> using vect = vector<T>;
class vec2 : public vector<vector<lint>>
{
public:
	vec2() {}
	vec2(lint n) : vector(n) {}
	vec2(lint h, lint w) : vector(h, vector<lint>(w)) {}
	vec2(lint h, lint w, lint v) : vector(h, vector<lint>(w, v)) {}
};

template<class T> using priq = priority_queue<T>;
template<class T> using rpriq = priority_queue<T, vector<T>, greater<T>>;
template<class Key, class Val> using hashmap = unordered_map<Key, Val>;
template<class Key> using hashset = unordered_set<Key>;

template<class It>
constexpr typename It::value_type rmax(It begin, It end) {
	return *max_element(begin, end);
}

template<class T1, class T2>
constexpr auto mmax(T1 arg1, T2 arg2) {
	using T = decltype(arg1 + arg2);
	return max(T(arg1), T(arg2));
}

template<class T, class ...Types>
constexpr auto mmax(T arg0, Types ...args) {
	return mmax(arg0, mmax(args...));
}

template<class It>
constexpr typename It::value_type rmin(It begin, It end) {
	return *min_element(begin, end);
}

template<class T1, class T2>
constexpr auto mmin(T1 arg1, T2 arg2) {
	using T = decltype(arg1 + arg2);
	return min(T(arg1), T(arg2));
}

template<class T, class ...Types>
constexpr auto mmin(T arg0, Types ...args) {
	return mmin(arg0, mmin(args...));
}

mt19937 mtrand((random_device())());

const double pi = 3.141592653589793238462;
const lint intmax = 9223372036854775807;
const lint inf = 1100100100100100100LL;

constexpr lint div2(lint p, lint q)
{
	return (p + q - 1) / q;
}

#if(__cplusplus < 201703L)

lint gcd(lint a, lint b) {
	while (1) {
		if (a < b) swap(a, b);
		if (!b) break;
		a %= b;
	}
	return a;
}

lint lcm(lint a, lint b)
{
	return a / gcd(a, b) * b;
}

#endif

template<class T>
struct nval {
	lint n;		// counts
	T val;
	nval() : n(0) {};
	nval(lint _n, T _val) : n(_n), val(_val) {};
};

template<class It, class It2>
auto spacel(It i, It2 end)
{
	if (i + 1 == end)
	{
		return '\n';
	}
	else
	{
		return ' ';
	}
}

ostream& setp(ostream& ost)
{
	cout << setprecision(60) << fixed;
	return ost;
}

const ulint mod = 1000000007;
//const ulint mod = 998244353;
const ld eps = 0.0000001;


struct graph
{
	struct R
	{
		lint to, c;
	};

	lint v, e;

	vector<vector<R>> gr;

	graph(lint _v) : v(_v), e(0), gr(v)
	{}

	void add_e(lint from, lint to, lint cost)
	{
		gr[from].push_back({ to, cost });
		e++;
	}

	auto dijkstra(lint start)
	{
		vector<lint> d(v, inf);

		d[start] = 0;

		struct Vc
		{
			lint pos, d;
			bool operator<(const Vc& p) const
			{
				return d > p.d;
			}
		};

		priority_queue<Vc> que;
		que.push({ start, 0 });

		while (!que.empty())
		{
			auto vc = que.top();
			que.pop();

			rep(i, gr[vc.pos].size())
			{
				if (vc.d + gr[vc.pos][i].c < d[gr[vc.pos][i].to])
				{
					d[gr[vc.pos][i].to] = vc.d + gr[vc.pos][i].c;
					que.push({ gr[vc.pos][i].to, d[gr[vc.pos][i].to] });
				}
			}
		}

		return d;
	}

};

char s[1010][1010];
lint h, w;

lint f(lint x, lint y) {
	return y * w + x;
}

template<class Tv, class Tl, class Tr>
bool between(Tv val, Tl l, Tr r) {
	return (val >= l) && (val <= r);
}

int main()
{
	cin >> h >> w;

	xy c, d;
	cin >> c.y >> c.x;
	cin >> d.y >> d.x;
	c.x--; c.y--;
	d.x--; d.y--;

	rep(i, h)
		cin >> s[i];

	graph g(h * w);

	rep(i, h)
		rep(j, w) {

		if (between(i + 1, 0, h - 1) && s[i + 1][j] == '.') {
			g.add_e(f(j, i), f(j, i + 1), 0);
		}
		if (between(i - 1, 0, h - 1) && s[i - 1][j] == '.') {
			g.add_e(f(j, i), f(j, i - 1), 0);
		}
		if (between(j + 1, 0, w - 1) && s[i][j + 1] == '.') {
			g.add_e(f(j, i), f(j + 1, i), 0);
		}
		if (between(j - 1, 0, w - 1) && s[i][j - 1] == '.') {
			g.add_e(f(j, i), f(j - 1, i), 0);
		}

		repb(dx, -2, 2)
			repb(dy, -2, 2) {
			if (between(i + dy, 0, h - 1) && between(j + dx, 0, w - 1) && s[i + dy][j + dx] == '.') {
				g.add_e(f(j, i), f(j + dx, i + dy), 1);
			}
		}
	}

	auto dd = g.dijkstra(f(c.x, c.y));

	lint ans = dd[f(d.x, d.y)];
	if (ans == inf) {
		cout << -1 << endl;
	}else
	cout << ans << endl;

	return 0;
}


Measured memory_bytes: 361180