#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
#include<sstream>
#include<iterator>
#include<list>

using namespace std;

typedef  long long int lint;

#define rep(i, n) for (lint i = 0; i < n; i++)
#define sort(v) sort((v).begin(), (v).end())
#define reverse(v) reverse((v).begin(), (v).end())
#define upper(v,hoge) upper_bound(v.begin(),v.end(),hoge)
#define lower(v,hoge) lower_bound(v.begin(),v.end(),hoge)
#define mp make_pair
#define P pair<int,int>
#define enld endl

int main() {
	const int INF = 1 << 30;
	const int di[4] = { 0,1,0,-1 };
	const int dj[4] = { 1,0,-1,0 };
	int h, w;
	cin >> h >> w;
	int sy, sx, gy, gx;
	cin >> sy >> sx >> gy >> gx;
	vector<string> field(h);
	for (int i = 0; i < h; i++) {
		cin >> field[i];
	}
	// BFS
	vector<vector<int> > d(h, vector<int>(w, INF));
	d[sy-1][sx-1] = 1;
	queue<P> que;
	que.push(P(sy-1, sx-1));

	while (!que.empty()) {
		P pos = que.front();
		que.pop();
		int i = pos.first, j = pos.second;
		for (int k = 0; k < 4; k++) {
			int ni = i + di[k], nj = j + dj[k];
			if (ni < 0 || ni >= h) continue;
			if (nj < 0 || nj >= w) continue;
			if (field[ni][nj] == '#') continue;
			if (d[ni][nj] > d[i][j] + 1) {
				d[ni][nj] = d[i][j] + 1;
				que.push(P(ni, nj));
			}
		}
	}
	if (d[gy - 1][gx - 1] == INF) {
		cout << -1 << endl;
	}
	else {
		cout << d[gy - 1][gx - 1]-1 << endl;
	}
}