#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <algorithm>
#include <iomanip>
#include <math.h>
#include <string.h>
#include <cstdio>
#include <tuple>
#include <numeric>
#include <functional>
using namespace std; using ll = long long; using ld = long double;  using pll = pair<ll, ll>;
using vl = vector<ll>; using vll = vector<vl>; using vlll = vector<vll>; using vpll = vector<pll>;
using vs = vector<string>; using tll = tuple<ll, ll, ll>; using vtll = vector<tll>;
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
const ld PI = 3.1415926535897932;
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define co(i) cout << i << endl;
#define co2(i,j) cout << i << " " << j << endl;
#define co3(i) cout << i << " ";
#define po(i) cout << i.first << " " << i.second << endl;
void in() {}
void debug_out() { cerr << endl; }
template<typename Head, typename... Tail>
void debug_out(Head h, Tail... t) {
	cerr << " " << h;
	if (sizeof...(t) > 0) cerr << " :";
	debug_out(t...);
}
template <typename T>
ostream& operator<<(ostream& os, vector<T> vec) {
	for (size_t i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
	return os;
}
ll ctoi(char c) {
	switch (c) {
	case '0': return 0; case '1': return 1; case '2': return 2;
	case '3': return 3; case '4': return 4; case '5': return 5;
	case '6': return 6; case '7': return 7; case '8': return 8;
	case '9': return 9;  default: return 0;
	}
}
bool pairCompare(const pll firstElof, pll secondElof)
{
	return firstElof.second < secondElof.second;
}
//**Snippetリスト**//
//rep, vin, all, iteLoop, bitSearch, bitList, nod, LIS, digitDP, treeDP, Rerooting//
//gcdlcm, isPrime, eratos, primeFactorize, Npow, combination, divisor, modinv, doubling//
//dfs, bfs, dijkstra, WarshallFloyd, BellmanFord, UnionFind, Kruskal, RMQ, LCA, FordFulkerson//
ll i, j, k, l; ll N, M, K, H, W, L, X, Y, Z, R, Q, T;
ll MOD = 1000000007, INF = 1LL << 60, ans = 0, z = 0, o = 1;
vll flag, D; vector<vpll> path; vs S;
void bfs(ll x,ll y) {
	priority_queue<tll> Q;
	Q.push(mt(0,x,y));
	D[x][y] = 0;
	ll q = -1;
	tll u;
	while (!Q.empty()) {
		u = Q.top();
		ll x = get<1>(u);
		ll y = get<2>(u);
		Q.pop();
		ll nx = x, ny = y;
		nx = x - 1; ny = y;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny]=='.') {
			if (D[x][y] < D[nx][ny]) {
				D[nx][ny] = D[x][y];
				Q.push(mt(D[nx][ny]*q,nx, ny));
			}
		}
		nx = x + 1; ny = y;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y] < D[nx][ny]) {
				D[nx][ny] = D[x][y];
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		nx = x; ny = y - 1;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y] < D[nx][ny]) {
				D[nx][ny] = D[x][y];
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		nx = x; ny = y + 1;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y] < D[nx][ny]) {
				D[nx][ny] = D[x][y];
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		//ここから魔法
		nx = x-1; ny = y-1;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y]+1 < D[nx][ny]) {
				D[nx][ny] = D[x][y]+1;
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		nx = x - 1; ny = y + 1;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y] + 1 < D[nx][ny]) {
				D[nx][ny] = D[x][y]+1;
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		nx = x + 1; ny = y - 1;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y] + 1 < D[nx][ny]) {
				D[nx][ny] = D[x][y]+1;
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		nx = x + 1; ny = y + 1;
		if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
			if (D[x][y] + 1 < D[nx][ny]) {
				D[nx][ny] = D[x][y]+1;
				Q.push(mt(D[nx][ny] * q, nx, ny));
			}
		}
		nx = x - 2;
		for (ll i = y - 2; i <= y + 2; i++) {
			ny = i;
			if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
				if (D[x][y] + 1 < D[nx][ny]) {
					D[nx][ny] = D[x][y]+1;
					Q.push(mt(D[nx][ny] * q, nx, ny));
				}
			}
		}
		nx = x + 2;
		for (ll i = y - 2; i <= y + 2; i++) {
			ny = i;
			if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
				if (D[x][y] + 1 < D[nx][ny]) {
					D[nx][ny] = D[x][y]+1;
					Q.push(mt(D[nx][ny] * q, nx, ny));
				}
			}
		}
		ny = y - 2;
		for (ll i = x - 1; i <= x + 1; i++) {
			nx = i;
			if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
				if (D[x][y] + 1 < D[nx][ny]) {
					D[nx][ny] = D[x][y]+1;
					Q.push(mt(D[nx][ny] * q, nx, ny));
				}
			}
		}
		ny = y + 2;
		for (ll i = x - 1; i <= x + 1; i++) {
			nx = i;
			if (nx >= 0 && nx < H && ny >= 0 && ny < W && S[nx][ny] == '.') {
				if (D[x][y] + 1 < D[nx][ny]) {
					D[nx][ny] = D[x][y]+1;
					Q.push(mt(D[nx][ny] * q, nx, ny));
				}
			}
		}
	}
}
int main() {
	cin >> H >> W;
	ll a,b,c,d;
	cin >> a >> b >> c >> d;
	a--; b--; c--; d--;
	S.resize(H);
	D.resize(H, vl(W,INF));
	for (i = 0; i < H; i++) {
		cin >> S[i];
	}
	bfs(a, b);
	if (D[c][d] == INF) cout << -1;
	else co(D[c][d]);
}







Measured memory_bytes: 13552