// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using namespace std::chrono;

#define ll long long
#define ull unsigned long long
#define FIO ios_base::sync_with_stdio(false);cin.tie(NULL);
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define ff first
#define ss second
#define vt vector
#define vll vt<ll>
#define pll pair<ll,ll>
#define vpll vt<pll>
#define vvll vt<vll>
#define all(v) v.begin(),v.end()
#define FOR(i,n) for(ll i=0;i<n;i++)
#define ffo(i,a,b) for(ll i=a;i<=b;i++)
#define rfo(i,a,b) for(ll i=a;i>=b;i--)
#define space cout<<"\n\n";
#define endl "\n"
#define pqmx priority_queue<ll>
#define pqmn priority_queue<ll,vll,greater<ll>>
#define fps(x,y) fixed<<setprecision(y)<<x
#define merg(a,b,c) set_union(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin()))
#define set_ar(arr,v) memset(arr,v,sizeof(arr))
#define go_t int testcases; cin>>testcases; ffo(caseno,1,testcases)

#define ctime auto start = high_resolution_clock::now()
#define etime auto stop = high_resolution_clock::now()
#define ptime auto z1z = duration_cast<microseconds>(stop-start); cout<<"Time elapsed : "<<z1z.count()<<" microseconds\n"

#define dbg1(x)             cout <<#x<<": "<<x<<'\n';
#define dbg2(x, y)          cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<'\n';
#define dbg3(x, y, z)       cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<'\n';
#define dbg4(a, b, c, d)    cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<'\n';
#define dbg5(a, b, c, d, e) cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<" | "<<#e<<": "<<e<<'\n';

const ll mod = 1e9 + 7;
const ll N = 6e4 + 6;
const ll maxN = 1e5 + 5;
const ll MAX_SIZE = 2e6 + 6;
const ll INF = 0x3f3f3f3f3f3f3f3fll;
const double PI = 3.14159265359;

int dx[4] = { -1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};
// up, right, down, left

ll powerM(ll x, ll y, ll M = mod) { // default argument
	ll v = 1; x = x % M; while (y > 0) {if (y & 1)v = (v * x) % M; y = y >> 1; x = (x * x) % M;} return v;
}

ll power(ll x, ll y) {
	ll v = 1; while (y > 0) {if (y & 1)v = v * x; y = y >> 1; x = x * x;} return v;
}

string a[1003];
ll val[1002][1002];
ll h, w;
ll ch, cw, dh, dw;
deque <pll> pq;

int main()
{
#ifndef ONLINE_JUDGE
	freopen("in4.txt", "r", stdin);
	freopen("out1.txt", "w", stdout);
#endif
	FIO
	FOR(i, 1002) {
		FOR(j, 1002) {
			val[i][j] = INF;
		}
	}
	cin >> h >> w;
	cin >> ch >> cw >> dh >> dw;
	FOR(i, h) {
		cin >> a[i];
	}
	--ch, --cw, --dh, --dw;
	val[ch][cw] = 0;
	pq.push_front({ch, cw});
	while (!pq.empty()) {
		auto tp = pq.front();
		pq.pop_front();
		ll x = tp.ff;
		ll y = tp.ss;
		for (int i = -2; i <= 2; i++) {
			for (int j = -2; j <= 2; j++) {
				int xx = x + i, yy = y + j;
				if (xx < 0 || yy < 0 || xx >= h || yy >= w || a[xx][yy] == '#')
					continue;
				if (i == 0 && j == 0)
					continue;
				int w = 1;
				if (abs(i) + abs(j) == 1)
					w = 0;
				// using 0-1 BFS
				if (val[x][y] + w < val[xx][yy]) {
					val[xx][yy] = val[x][y] + w;
					if (w == 0)
						pq.push_front({xx, yy});
					else
						pq.push_back({xx, yy});
				}
			}
		}
	}
	if (val[dh][dw] == INF) {
		val[dh][dw] = -1;
	}
	cout << val[dh][dw];
	return 0;
}


Measured memory_bytes: 12692