#include <iostream>
#include <array>
#include <algorithm>
#include <map>
#include <vector>
#include <list>
#include <cmath>
#include <stack>
#include <queue>
#include <climits>
#include <string.h>
#include <cctype>
#include <set>

#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int, int>;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }

// a と b の最大公約数を返す関数
long long GCD(long long a, long long b) {
	if (b == 0) return a;
	else return GCD(b, a % b);
}

long long gcd(long long a, long long b)
{
	if (a % b == 0)
	{
		return(b);
	}
	else
	{
		return(gcd(b, a % b));
	}
}

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

// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
const int mod = 1000000007;
struct mint {
	ll x; // typedef long long ll;
	mint(ll x = 0) :x((x% mod + mod) % mod) {}
	mint operator-() const { return mint(-x); }
	mint& operator+=(const mint a) {
		if ((x += a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator-=(const mint a) {
		if ((x += mod - a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this; }
	mint operator+(const mint a) const { return mint(*this) += a; }
	mint operator-(const mint a) const { return mint(*this) -= a; }
	mint operator*(const mint a) const { return mint(*this) *= a; }
	mint pow(ll t) const {
		if (!t) return 1;
		mint a = pow(t >> 1);
		a *= a;
		if (t & 1) a *= *this;
		return a;
	}

	// for prime mod
	mint inv() const { return pow(mod - 2); }
	mint& operator/=(const mint a) { return *this *= a.inv(); }
	mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream& operator>>(istream& is, const mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }

struct combination {
	vector<mint> fact, ifact;
	combination(int n) :fact(n + 1), ifact(n + 1) {
		fact[0] = 1;
		for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
		ifact[n] = fact[n].inv();
		for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
	}
	mint operator()(int n, int k) {
		if (k < 0 || k > n) return 0;
		return fact[n] * ifact[k] * ifact[n - k];
	}
} comb(2000005);

mint g(int r, int c) {
	return comb(r + c + 2, r + 1) - 1;
}

bool comp(int i, int j) {
	return i > j;
}

bool compare_by_b(pair<int, int> a, pair<int, int> b) {
	return a.second < b.second;
}

long tall[200000];
long long diff[200000];
vector<int> que;

// index が条件を満たすかどうか
bool isOK(int index, int key) {
	if (que[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)que.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;
	}
	return res;
}

int kind[1000][1000];
int area[1000][1000];
int h, w;
int sh, sw;
int gh, gw;
vector<vector<int>> uni;
queue<pair<int, int>> nn;
vector<int> shortCount;
queue<pair<int, int>> nextArea;


bool isArea(int y, int x)
{
	return x >= 0 && y >= 0 && y < h && x < w;
}

int main()
{
	cin >> h >> w;
	cin >> sh >> sw;
	cin >> gh >> gw;

	for (int i = 0; i < h; i++)
	{
		string s;
		cin >> s;
		for (int j = 0; j < w; j++)
		{
			kind[i][j] = (s[j] == '#' ? -1 : 0);
			//kind[i][j] = ((i + j) % 2 == 0 ? 0 : -1);
			area[i][j] = -1;
		}
	}

	int areaCount = 1;
	uni.push_back({});

	for (int i = 0; i < h; i++)
	{
		for (int j = 0; j < w; j++)
		{
			if (kind[i][j] == -1)
			{
				continue;
			}

			if (area[i][j] != -1)
			{
				continue;
			}

			uni.push_back({});

			nn.push(make_pair(i, j));
			while (nn.size() > 0)
			{
				pair<int, int> check = nn.front();
				nn.pop();
				if (kind[check.first][check.second] == -1)
				{
					continue;
				}
				if (area[check.first][check.second] != -1)
				{
					continue;
				}

				area[check.first][check.second] = areaCount;

				if (isArea(check.first + 1, check.second))
				{
					nn.push(make_pair(check.first + 1, check.second));
				}

				if (isArea(check.first - 1, check.second))
				{
					nn.push(make_pair(check.first - 1, check.second));
				}

				if (isArea(check.first, check.second + 1))
				{
					nn.push(make_pair(check.first, check.second + 1));
				}

				if (isArea(check.first, check.second - 1))
				{
					nn.push(make_pair(check.first, check.second - 1));
				}
			}

			areaCount++;
		}
	}

	for (int i = 0; i < h; i++)
	{
		for (int j = 0; j < w; j++)
		{
			int a = area[i][j];
			if (a == -1)
			{
				continue;
			}

			for (int k = -2; k <= 2; k++)
			{
				for (int l = -2; l <= 2; l++)
				{
					if (k == 0 && l == 0)
					{
						continue;
					}
					if (!isArea(i + k, j + l))
					{
						continue;
					}

					if (area[i + k][j + l] == -1)
					{
						continue;
					}

					if (a == area[i + k][j + l])
					{
						continue;
					}

					uni[a].push_back(area[i + k][j + l]);
					uni[area[i + k][j + l]].push_back(a);
				}
			}
		}
	}

	for (int i = 0; i < areaCount; i++)
	{
		shortCount.push_back(-1);
		unique(uni[i].begin(), uni[i].end());
	}

	nextArea.push(make_pair(area[sh - 1][sw - 1], 0));
	while (nextArea.size() > 0)
	{
		pair<int, int> sa = nextArea.front();
		nextArea.pop();

		if (shortCount[sa.first] != -1)
		{
			continue;
		}
		shortCount[sa.first] = sa.second;

		if (sa.first == area[gh - 1][gw - 1])
		{
			cout << sa.second;
			return 0;
		}

		for (int i = 0; i < uni[sa.first].size(); i++)
		{
			nextArea.push(make_pair(uni[sa.first][i], sa.second + 1));
		}
	}

	cout << -1;
}


Measured memory_bytes: 66288