#include <bits/stdc++.h>
using namespace std;

#define ms(s, n) memset(s, n, sizeof(s))
#define f(i, a, b) for (int i = (a); i <=(b); i++)
#define FORd(i, a, b) for (int i = (a) - 1; i >= (b); i--)
#define FORall(it, a) for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed<<setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<ll> vi;
typedef vector<pi> vii;
const int MOD = (int) 1e9 + 7;
const int MOD2 = MOD + 2; //1007681537;
const int INF = (int) 1e9;
const ll LINF = (ll) 1e18;
const ld PI = acos((ld) - 1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {ll r; while (b) {r = a % b; a = b; b = r;} return a;}
inline ll lcm(ll a, ll b) {return a / gcd(a, b) * b;}
inline ll fpow(ll n, ll k, int p = MOD) {ll r = 1; for (; k; k >>= 1) {if (k & 1) r = r * n % p; n = n * n % p;} return r;}
template<class T> inline int chkmin(T& a, const T& val) {return val < a ? a = val, 1 : 0;}
template<class T> inline int chkmax(T& a, const T& val) {return a < val ? a = val, 1 : 0;}
inline ll isqrt(ll k) {ll r = sqrt(k) + 1; while (r * r > k) r--; return r;}
inline ll icbrt(ll k) {ll r = cbrt(k) + 1; while (r * r * r > k) r--; return r;}
inline void addmod(int& a, int val, int p = MOD) {if ((a = (a + val)) >= p) a -= p;}
inline void submod(int& a, int val, int p = MOD) {if ((a = (a - val)) < 0) a += p;}
inline int mult(int a, int b, int p = MOD) {return (ll) a * b % p;}
inline int inv(int a, int p = MOD) {return fpow(a, p - 2, p);}
inline int sign(ld x) {return x < -EPS ? -1 : x > +EPS;}
inline int sign(ld x, ld y) {return sign(x - y);}
int modulo(int a, int b) { return (a % b + b) % b; }
#define db(x) cerr << #x << " = " << (x) << " ";
#define endln cerr << "\n";

int h, w, ch, cw, dh, dw;
int ans = 0;
vector<int>dx = {0, 0, 1, -1}, dy = {1, -1, 0, 0};
bool ok(int x, int y) {
	if (x >= 0 && x < h && y >= 0 && y < w) {
		return true;
	}
	return false;
}
int main() {
	IOS;
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif
	cin >> h >> w >> ch >> cw >> dh >> dw;
	vector<string> s(h);
	f(i, 0, h - 1) {
		cin >> s[i];
	}
	ch--; cw--; dh--; dw--;
	vector<vector<bool>>vis(h, vector<bool>(w, 0));
	vector<vi>dist(h, vi(w, LINF));
	deque<pi>q;
	q.push_front({ch, cw});
	dist[ch][cw] = 0;
	while (!q.empty()) {
		pi p = q.front();
		q.pop_front();
		if (vis[p.fi][p.se])
			continue;
		vis[p.fi][p.se] = 1;
		f(k, 0, 3) {
			int newx = p.fi + dx[k];
			int newy = p.se + dy[k];
			if (ok(newx, newy) && s[newx][newy] != '#') {
				q.push_front({newx, newy});
				dist[newx][newy] = dist[p.fi][p.se];
			}
		}
		f(i, p.fi - 2 , p.fi + 2) {
			f(j, p.se - 2, p.se + 2) {
				if (ok(i, j) && s[i][j] != '#') {
					dist[i][j] = min(dist[p.fi][p.se] + 1, dist[i][j]);
					q.push_back({i, j});
					//vis[i][j] = 1;
				}
			}
		}
	}
	cout << (dist[dh][dw] == LINF ? -1 : dist[dh][dw]) << endl;
	// read the stuff at the bottom
	return 0;
}
/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?)
	* do smth instead of nothing and stay organized
	* WRITE STUFF DOWN
	* use int when constraints limits are tight
	* Time taken : global variable < pass by refernce < pass by value
	* It takes significant amt. of time in pass by value
*/





























Measured memory_bytes: 13592