#include "bits/stdc++.h"
using namespace std;
const int MAX = 700000;
const int 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;
	}
}

// 二項係数計算
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;
}
/*第二引数で第一引数を割ったときの切り上げの計算*/
long long int maxtime(long long int x, long long int y) {
	return(x + y - 1) / y;

}
/*最大公約数*/
long long int lcm(long long int number1, long long int number2) {
	long long int m = number1;
	long long int n = number2;

	if (number2 > number1) {
		m = number2;
		n = number1;
	}
	long long int s = -1;
	while (s != 0) {
		s = m % n;
		m = n;
		n = s;
	}
	return m;
}
/*最大公倍数*/
long long int gcd(long long int number1, long long int number2) {
	long long int m = number1;
	long long int n = number2;
	return m / lcm(m, n) * n;
}
/*逆元計算*/
long long int  modinv(long long a, long long m) {
	long long int b = m, u = 1, v = 0;
	while (b) {
		long long int t = a / b;
		a -= t * b; swap(a, b);
		u -= t * v; swap(u, v);
	}
	u %= m;
	if (u < 0) u += m;
	return u;
}
// index が条件を満たすかどうか
vector<long long int >meguru;
bool isOK(int index, int key) {
	if (meguru[index] >= key) return true;
	else return false;
}
// 汎用的な二分探索のテンプレ
int binary_search(int key) {
	int left = -1; //「index = 0」が条件を満たすこともあるので、初期値は -1
	int right = (int)meguru.size(); // 「index = a.size()-1」が条件を満たさないこともあるので、初期値は a.size()
	/* どんな二分探索でもここの書き方を変えずにできる！ */
	while (right - left > 1) {
		int mid = left + (right - left) / 2;

		if (isOK(mid, key)) right = mid;
		else left = mid;
	}
	/* left は条件を満たさない最大の値、right は条件を満たす最小の値になっている */
	return right;
}
long long modpow(long long a, long long n, long long mod) {
	long long res = 1;
	while (n > 0) {
		if (n & 1) res = res * a % mod;
		a = a * a % mod;
		n >>= 1;
	}
	return res;
}
char masu[1030][1030] = {};
int  sinko[1030][1030] = {};
int  o[1030][1030] = {};
queue<pair<int, int>>q;
queue<pair<int, int>>s;
int main() {
	int h, w;
	cin >> h >> w;
	int ch, cw, dh, dw;
	cin >> ch >> cw >> dh >> dw;
	int x[4] = { 1,-1,0,0 };
	int y[4] = { 0,0,1,-1 };
	for (int i = 0; i < h; i++) {
		for (int j = 0; j < w; j++) {
			char a;
			cin >> a;
			masu[i][j] = a;
		}
	}
	q.push(make_pair(cw - 1, ch - 1));
	sinko[ch - 1][cw - 1] = 1;
	o[ch - 1][cw - 1] = 1;
	int b = 1;
	while (b == 1) {
		b = 0;
		while (q.size()) {
			int x1, y1;
			x1 = q.front().first;
			y1 = q.front().second;
			s.push(make_pair(x1, y1));
			q.pop();
			for (int i = 0; i < 4; i++) {
				if (x1 + x[i] >= 0 && x1 + x[i] < w && y1 + y[i] >= 0 && y1 + y[i] < h) {
					if (masu[y1 + y[i]][x1 + x[i]] != '#') {
						if (sinko[y1 + y[i]][x1 + x[i]] == 0) {
							q.push(make_pair(x1 + x[i], y1 + y[i]));
							s.push(make_pair(x1 + x[i], y1 + y[i]));
							sinko[y1 + y[i]][x1 + x[i]] = 1;
							o[y1 + y[i]][x1 + x[i]] = o[y1][x1];
						}
					}
				}
			}
		}
		while (s.size()) {
			int i = s.front().second;
			int j = s.front().first;
			s.pop();
			for (int k = -2; k <= 2; k++) {
				for (int l = -2; l <= 2; l++) {
					if (i + k >= 0 && i + k < h && j + l >= 0 && j + l < w && sinko[i + k][j + l] == 0 && masu[i + k][j + l] != '#') {
						q.push(make_pair(j + l, i + k));
						o[i + k][j + l] = o[i][j] + 1;
						sinko[i + k][j + l] = 1;
						b = 1;
					}
				}
			}

		}
	}

	if (o[dh - 1][dw - 1] == 0) {
		cout << -1;
	}
	else {
		cout << o[dh - 1][dw - 1] - 1;
	}
}

Measured memory_bytes: 12636