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

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define REP1(i,n) for(int i=1, i##_len=(n); i<i##_len; ++i)
#define ll long long
static const ll MAX = 10000;
static const ll INFTY = 1e12;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

// 四方向への移動ベクトル
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
using P = pair<ll, ll>;
// 入力
// 入力
ll h, w;
ll startX, startY, endX, endY;
vector<vector<char>> s;
vector<vector<ll>> cnts; // 魔法使った回数

void bfs(){

    queue<P> q, visited;
    q.push(P(startX, startY));
    cnts[startX][startY] = 0;

    while (!q.empty() || !visited.empty()) {
        ll nowX, nowY;
        if (!q.empty()) {
            nowX = q.front().first, nowY = q.front().second;
            visited.push(P(nowX, nowY));
            q.pop();
            REP(i, 4) {
                ll nextX = nowX + dx[i], nextY = nowY + dy[i];
                if (0 <= nextX && nextX <= h - 1 && 0 <= nextY && nextY <= w - 1) {
                    if (s[nextX][nextY] == '#') continue;
                    if (cnts[nowX][nowY] < cnts[nextX][nextY]) {
                        cnts[nextX][nextY] = cnts[nowX][nowY];
                        q.push(P(nextX, nextY));
                    }
                }
            }

        } else {  // 今まで通った道から魔法で行ける道を全て調べる
            nowX = visited.front().first, nowY = visited.front().second;
            visited.pop();
            for (ll ix = -2; ix <= 2; ++ix) {
                for (ll jy = -2; jy <= 2; ++jy) {
                    ll nextX = nowX + ix, nextY = nowY + jy;
                    if (0 <= nextX && nextX <= h - 1 && 0 <= nextY && nextY <= w - 1) {
                        if (s[nextX][nextY] == '#') continue;
                        if (cnts[nowX][nowY] + 1 < cnts[nextX][nextY]) {
                            cnts[nextX][nextY] = cnts[nowX][nowY] + 1;
                            q.push(P(nextX, nextY));
                        }
                    }
                }
            }
        }
    }

}

int main() {
    
    cin >> h >> w;
    cin >> startX >> startY >> endX >> endY;
    startX--, startY--, endX--, endY--;
    s.assign(h, vector<char>(w));
    REP(i, h) REP(j, w) cin >> s[i][j];
    cnts.assign(h, vector<ll>(w, INFTY));

    bfs();

    // REP(i, h){
    //    REP(j, w){
    //        cout << cnts[i][j] << " ";
    //    } cout << endl;
    // }

    if (cnts[endX][endY] == INFTY) {
        cout << -1 << '\n';
    } else {
        cout << cnts[endX][endY] << '\n';
    }
    return 0;
}
/*
                   _ooOoo_
                  o8888888o
                  88" . "88
                  (| -_- |)
                  O\  =  /O
               ____/`---'\____
             .'  \\|     |//  `.
            /  \\|||  :  |||//  \
           /  _||||| -:- |||||-  \
           |   | \\\  -  /// |   |
           | \_|  ''\---/''  |   |
           \  .-\__  `-`  ___/-. /
         ___`. .'  /--.--\  `. . __
      ."" '<  `.___\_<|>_/___.'  >'"".
     | | :  `- \`.;`\ _ /`;.`/ - ` : | |
     \  \ `-.   \_ __\ /__ _/   .-` /  /
======`-.____`-.___\_____/___.-`____.-'======
                   `=---='
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         pass System Test!
*/

Measured memory_bytes: 12520