#include <bits/stdc++.h>
#define INF 999999999
#define N 2000
#define mkp(a,b) make_pair(a,b)
#define sz(c) (int)(c).size()
using namespace std;
int h , w , ch , cw , dh , dw , dp[N][N] , ans = INF;
char a[N][N];
int movex[] = {1 , 0 , -1 , 0};
int movey[] = {0 , 1 , 0 , -1};
queue < pair<int,int> > q;
bool check(int x , int y){
    if(x < 0 || y < 0) return 0;
    if(x >= h || y >= w) return 0;
    return 1;
}
int main(){
    cin >> h >> w;
    cin >> ch >> cw;
    cin >> dh >> dw;
    dh--; dw--;
    ch--; cw--;
    for(int i = 0 ; i < h ; i++){
        for(int j = 0 ;j < w ; j++) cin >> a[i][j];
    }
    for(int i = 0 ; i < h ; i++){
        for(int j = 0 ; j < w ; j++){
            dp[i][j] =INF;
        }
    }
    dp[ch][cw] = 0;
    q.push(mkp(ch,cw));
    while(sz(q) > 0){
        pair<int,int> p = q.front();
        int x = p.first , y = p.second;
        q.pop();
        for(int i = x-2 ; i <= x + 2 ; i++){
                for(int j = y-2 ; j <= y+2 ; j++){
                    if(!check(i,j)) continue;
                    int d = abs(i-x) + abs(j-y) <= 1 ? 0 : 1;
                    if(a[i][j]=='.' && dp[i][j]>dp[x][y]+d) {
                        dp[i][j] = dp[x][y] + d;
                        q.push(mkp(i,j));
                    }
                }
        }
    }
    if(dp[dh][dw] == INF) cout <<"-1";
    else cout << dp[dh][dw] << '\n';

}