/*
このコード、と～おれ!
Be accepted!
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		  　　　　　　　　　　(¸.·´ (¸.·'* ☆
*/

#include <cstdio>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstring>
#include <vector>
#include <numeric>
#include <iostream>
#include <random>
#include <map>
#include <unordered_map>
#include <queue>
#include <regex>
#include <functional>
#include <complex>
#include <list>
#include <cassert>
#include <iomanip>
#include <set>
#include <stack>
#include <bitset>

////多倍長整数, cpp_intで宣言
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision;

//#pragma GCC target ("avx2")
//#pragma GCC optimization ("Ofast")
//#pragma GCC optimization ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define repeat(i, n, m) for(int i = n; i < (m); ++i)
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define printynl(a) printf(a ? "yes\n" : "no\n")
#define printyn(a) printf(a ? "Yes\n" : "No\n")
#define printYN(a) printf(a ? "YES\n" : "NO\n")
#define printim(a) printf(a ? "possible\n" : "imposible\n")
#define printdb(a) printf("%.50lf\n", a) //少数出力
#define printLdb(a) printf("%.50Lf\n", a) //少数出力
#define printdbd(a) printf("%.16lf\n", a) //少数出力(桁少なめ)
#define prints(s) printf("%s\n", s.c_str()) //string出力
#define all(x) (x).begin(), (x).end()
#define deg_to_rad(deg) (((deg)/360.0L)*2.0L*PI)
#define rad_to_deg(rad) (((rad)/2.0L/PI)*360.0L)
#define Please return
#define AC 0
#define manhattan_dist(a, b, c, d) (abs(a - c) + abs(b - d)) /*(a, b) から (c, d) のマンハッタン距離 */
#define inf numeric_limits<double>::infinity();
#define linf numeric_limits<long double>::infinity()

using ll = long long;
using ull = unsigned long long;

constexpr int INF = 1073741823;
constexpr int MINF = -1073741823;
constexpr ll LINF = ll(4661686018427387903);
constexpr ll MOD = 1e9 + 7;
constexpr ll mod = 998244353;
constexpr long double eps = 1e-6;
const long double PI = acosl(-1.0L);

using namespace std;

void scans(string& str) {
	char c;
	str = "";
	scanf("%c", &c);
	if (c == '\n')scanf("%c", &c);
	while (c != '\n' && c != -1 && c != ' ') {
		str += c;
		scanf("%c", &c);
	}
}

void scanc(char& str) {
	char c;
	scanf("%c", &c);
	if (c == -1)return;
	while (c == '\n') {
		scanf("%c", &c);
	}
	str = c;
}


double acot(double x) {
	return PI / 2 - atan(x);
}

ll LSB(ll n) { return (n & (-n)); }

template<typename T>
inline T chmin(T& a, const T& b) {
	if (a > b)a = b;
	return a;
}

template<typename T>
inline T chmax(T& a, const T& b) {
	if (a < b)a = b;
	return a;
}

/*-----------------------------------------ここからコード-----------------------------------------*/

queue<pair<int, int>> que;

void dfs(const vector<string>& s, const int& ny, const int& nx, vector<vector<int>> &dp, const int &h, const int &w, vector<vector<bool>> &visited) {
	visited[ny][nx] = true;
	for (int i = max(0, ny - 2); i < h and i <= ny + 2; ++i) {
		for (int j = max(0, nx - 2); j < w and j <= nx + 2; ++j) {
			if (dp[i][j] == dp[ny][nx] + 1 or dp[i][j] == INF)que.push({ i, j });
			chmin(dp[i][j], dp[ny][nx] + 1);
		}
	}
	if (ny != h - 1 and not visited[ny + 1][nx]) {
		chmin(dp[ny + 1][nx], dp[ny][nx]);
		dfs(s, ny + 1, nx, dp, h, w, visited);
	}
	if (ny != 0 and not visited[ny - 1][nx]) {
		chmin(dp[ny - 1][nx], dp[ny][nx]);
		dfs(s, ny - 1, nx, dp, h, w, visited);
	}
	if (nx != w - 1 and not visited[ny][nx + 1]) {
		chmin(dp[ny][nx + 1], dp[ny][nx]);
		dfs(s, ny, nx + 1, dp, h, w, visited);
	}
	if (nx != 0 and not visited[ny][nx - 1]) {
		chmin(dp[ny][nx - 1], dp[ny][nx]);
		dfs(s, ny, nx - 1, dp, h, w, visited);
	}
}

int main() {

	int h, w, ch, cw, dh, dw;
	scanf("%d%d%d%d%d%d", &h, &w, &ch, &cw, &dh, &dw);
	--ch, --cw, --dh, --dw;
	vector<string> s(h);
	rep(i, h)scans(s[i]);
	vector<vector<int>> dp(h, vector<int>(w));
	vector<vector<bool>> visited(h, vector<bool>(w));
	rep(i, h)fill(all(dp[i]), INF);
	rep(i, h) {
		rep(j, w) {
			if (s[i][j] == '#')visited[i][j] = true;
		}
	}
	dp[ch][cw] = 0;
	que.push({ ch, cw });
	while (not que.empty()) {
		auto [yy, xx] = que.front();
		que.pop();
		if (visited[yy][xx])continue;
		dfs(s, yy, xx, dp, h, w, visited);
	}
	printf("%d\n", dp[dh][dw] == INF ? -1 : dp[dh][dw]);

	Please AC;
}


Measured memory_bytes: 10488