#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <tuple>
#include <cstdint>
#include <cstdio>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <bitset>
#include <cctype>
#include <math.h>
#include <cmath>
#include <ctime>
#include <stdlib.h>


using namespace std;

/*
#pragma GCC target("avx2") //AtCoderでは "avx" にする
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
*/

#define int long long
#define endl "\n"
#define all(v)  v.begin(),v.end()
#define fir first
#define sec second
#define m_p make_pair
#define m_t make_tuple
#define rep(i,n)  for(int i=0; i<(int) (n); i++)
typedef pair<int, int> P;
typedef long double ld;
typedef long long ll;
template<class T> using PQ_inv = priority_queue<T, vector<T>, greater<T>>;

const double pai = 3.1415926535897;
const ll mod = 1000000007;
const int INF = 1000000021;
const ll LINF = 2000000000000000000;
const int MAX = 510000;
const ll MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];


// テーブルを作る前処理
void COMinit() {
	fac[0] = fac[1] = 1;
	finv[0] = finv[1] = 1;
	inv[1] = 1;
	for (int i = 2; i < MAX; i++) {
		fac[i] = fac[i - 1] * i % MOD;
		inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
		finv[i] = finv[i - 1] * inv[i] % MOD;
	}
}
//n個を1個以上のx組のグループに分ける重複組み合わせはcom(n-1,x-1)
long long COM(int n, int k) {
	if (n < k) return 0;
	if (n < 0 || k < 0) return 0;
	return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
ll PER(int n, int k) {
	if (n < 0 || k < 0) return 0;
	if (n < k) return fac[n];
	return fac[n] * finv[n - k] % mod;
}

long long modinv(long long a, long long m) {
	long long b = m, u = 1, v = 0;
	while (b) {
		long long t = a / b;
		a -= t * b; swap(a, b);
		u -= t * v; swap(u, v);
	}
	u %= m;
	if (u < 0) u += m;
	return u;
}
long long modpow(int a, int n) {
	int res = 1;
	while (n > 0) {
		if (n & 1) res = res * a % mod;
		a = a * a % mod;
		n >>= 1;
	}
	return res;
}


struct edge {
	int to, cost;
};
edge m_e(int xx, int yy) {
	edge ed;
	ed.to = xx;
	ed.cost = yy;
	return ed;
}
//x未満の要素数を返す二分探索関数
int b_s(vector<int>& vec, int xx) {
	return lower_bound(all(vec), xx) - vec.begin();
}
template<class T>void vecout(vector<T>& vec) { for (T t : vec) cout << t << " "; cout << endl; }
template<class T>void vecin(vector<T>& vec) { for (int i = 0; i < vec.size(); i++) cin >> vec[i]; }
bool chmax(int& xx, int yy) {
	if (xx < yy) {
		xx = yy;
		return true;
	}
	return false;
}
bool chmin(int& xx, int yy) {
	if (xx > yy) {
		xx = yy;
		return true;
	}
	return false;
}
double dist(int x, int y) {
	return sqrt(x * x + y * y);
}
double dist(int xx1, int xx2, int yy1, int yy2) {
	return sqrt(abs(xx1 - xx2) * abs(xx1 - xx2) + abs(yy1 - yy2) * abs(yy1 - yy2));
}
ll mypow(int nn, int kk) {
	ll xx = 1;
	rep(i, kk) {
		xx *= nn;
	}
	return xx;
}
int gcd(int xx, int yy) {
	int p = xx;
	int q = yy;
	if (q > p)swap(p, q);
	while (p % q != 0) {
		p %= q;
		swap(p, q);
	}
	return q;
}
int lcm(int xx, int yy) {
	return xx * yy / gcd(xx, yy);
}
bool prime(int xx) {
	if (xx <= 1) {
		return 0;
	}
	for (int i = 2; i * i <= xx; i++) {
		if (xx % i == 0) {
			return 0;
		}
	}
	return 1;
}



signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int h, w, cx, cy, dx, dy, c = 0;
	queue<P>que;
	cin >> h >> w >> cy >> cx >> dy >> dx;
	cx--;
	cy--;
	dx--;
	dy--;
	vector<vector<char>>vec(h, vector<char>(w, 'x'));
	rep(i, h) {
		rep(j, w) {
			cin >> vec[i][j];
		}
	}
	{
		queue<P>que2;
		vector<P>vec2;
		que2.push(m_p(cy, cx));
		while (!que2.empty()) {
			int fi = que2.front().first, se = que2.front().second;
			que2.pop();
			if (fi == dy && se == dx) {
				cout << 0 << endl;
				return 0;
			}
			vec2.push_back(m_p(fi, se));
			vec[fi][se] = 'o';
			if (fi > 0 && vec[fi - 1][se] == '.') {
				vec[fi - 1][se] = 'o';
				que2.push(m_p(fi - 1, se));
			}
			if (fi < h - 1 && vec[fi + 1][se] == '.') {
				vec[fi + 1][se] = 'o';
				que2.push(m_p(fi + 1, se));
			}
			if (se > 0 && vec[fi][se - 1] == '.') {
				vec[fi][se - 1] = 'o';
				que2.push(m_p(fi, se - 1));
			}
			if (se < w - 1 && vec[fi][se + 1] == '.') {
				vec[fi][se + 1] = 'o';
				que2.push(m_p(fi, se + 1));
			}
		}
		for (P p : vec2) {
			for (int i = p.first - 2; i < p.first + 3; i++) {
				if (i < 0 || i >= h)continue;
				for (int j = p.second - 2; j < p.second + 3; j++) {
					if (j < 0 || j >= w)continue;
					if (vec[i][j] == '.') {
						que.push(m_p(i, j));
					}
				}
			}
		}
	}
	/*
	rep(i, h) {
		rep(j, w) {
			cout << vec[i][j];
		}
		cout << endl;
	}
	*/
	while (1) {
		c++;
		if (que.empty()) {
			cout << -1 << endl;
			return 0;
		}
		vector<P>vec2;
		while (!que.empty()) {
			int fi = que.front().first, se = que.front().second;
			que.pop();
			if (fi == dy && se == dx) {
				cout << c << endl;
				return 0;
			}
			vec2.push_back(m_p(fi, se));
			vec[fi][se] = 'o';
			if (fi > 0 && vec[fi - 1][se] == '.') {
				vec[fi - 1][se] = 'o';
				que.push(m_p(fi - 1, se));
			}
			if (fi < h - 1 && vec[fi + 1][se] == '.') {
				vec[fi + 1][se] = 'o';
				que.push(m_p(fi + 1, se));
			}
			if (se > 0 && vec[fi][se - 1] == '.') {
				vec[fi][se - 1] = 'o';
				que.push(m_p(fi, se - 1));
			}
			if (se < w - 1 && vec[fi][se + 1] == '.') {
				vec[fi][se + 1] = 'o';
				que.push(m_p(fi, se + 1));
			}
		}
		for (P p : vec2) {
			for (int i = p.first - 2; i < p.first + 3; i++) {
				if (i < 0 || i >= h)continue;
				for (int j = p.second - 2; j < p.second + 3; j++) {
					if (j < 0 || j >= w)continue;
					if (vec[i][j] == '.') {
						que.push(m_p(i, j));
					}
				}
			}
		}
	}
}

Measured memory_bytes: 20288