#include <bits/stdc++.h>
 
using namespace std;
 
#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl;
#define DEBUG_MAT(v) cerr<<#v<<endl;for(int i=0;i<v.size();i++){for(int j=0;j<v[i].size();j++) {cerr<<v[i][j]<<" ";}cerr<<endl;}
typedef long long ll;
#define int ll
 
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define X first
#define Y second
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define rrep1(i,n) for(int i=(int)(n);i>0;i--)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(),c.end()
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const long double pi = 3.1415926535897932384626433832795028841971L;
#define Sp(p) cout<<setprecision(25)<< fixed<<p<<endl;
// int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
// int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
vi dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
// vi dx2 = { 1,1,0,-1,-1,-1,0,1 }, dy2 = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);
const ll MOD = 1000000007;
// const ll MOD = 998244353;
// #define mp make_pair
//#define endl '\n'



signed main() {
    fio();
    
    int h, w;
    cin >> h >> w;
    int sy, sx, gy, gx;
    cin >> sy >> sx >> gy >> gx;
    sy--; sx--; gy--; gx--;

    vector<string> s(h);
    rep (i, h) cin >> s[i];
    vii dist(h, vi(w, inf));
    dist[sy][sx] = 0;

    queue<pii> qu0, qu1;
    qu0.push(pii(sy, sx));
    while (qu0.size() > 0 or qu1.size() > 0) {
        while (qu0.size() > 0) {
            pii temp = qu0.front();
            qu0.pop();
            int y = temp.first, x = temp.second;

            rep (k, 4) {
                int ny = y + dy[k], nx = x + dx[k];
                if (not in(ny, 0, h) or not in(nx, 0, w)) continue;
                if (s[ny][nx] == '#') continue;
                if (dist[ny][nx] > dist[y][x]) {
                    dist[ny][nx] = dist[y][x];
                    qu0.push(pii(ny, nx));
                }
            }

            for (int dy = -2; dy <= 2; dy++) {
                for (int dx = -2; dx <= 2; dx++) {
                    int ny = y + dy, nx = x + dx;
                    if (not in(ny, 0, h) or not in(nx, 0, w)) continue;
                    if (s[ny][nx] == '#') continue;
                    if (dist[ny][nx] > dist[y][x] + 1) {
                        dist[ny][nx] = dist[y][x] + 1;
                        qu1.push(pii(ny, nx));
                    }
                }
            }
        }

        if (qu1.size() > 0) {
            pii temp = qu1.front();
            qu1.pop();
            int y = temp.first, x = temp.second;

            rep (k, 4) {
                int ny = y + dy[k], nx = x + dx[k];
                if (not in(ny, 0, h) or not in(nx, 0, w)) continue;
                if (s[ny][nx] == '#') continue;
                if (dist[ny][nx] > dist[y][x]) {
                    dist[ny][nx] = dist[y][x];
                    qu0.push(pii(ny, nx));
                }
            }

            for (int dy = -2; dy <= 2; dy++) {
                for (int dx = -2; dx <= 2; dx++) {
                    int ny = y + dy, nx = x + dx;
                    if (not in(ny, 0, h) or not in(nx, 0, w)) continue;
                    if (s[ny][nx] == '#') continue;
                    if (dist[ny][nx] > dist[y][x] + 1) {
                        dist[ny][nx] = dist[y][x] + 1;
                        qu1.push(pii(ny, nx));
                    }
                }
            }
        }
    }

    if (dist[gy][gx] == inf) cout << -1 << endl;
    else cout << dist[gy][gx] << endl;
}

Measured memory_bytes: 12784