#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(int i=0;i<n;i++)
#define ALL(v) v.begin(),v.end()
constexpr ll MOD=998244353;
constexpr ll INF=1e18;

struct xy {
    int x; int y; int d;
    bool operator<(const xy &another) const {return d > another.d;};
};
int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 };
int h, w;
vector<string> s(1333);

ll bfs(int sx, int sy, int gx, int gy){
    priority_queue<xy> q;
    q.push({sx,sy,0});
    VVI dis(h,VI(w,INF)); dis[sx][sy]=0;
    vector<vector<xy>> from(h,vector<xy>(w,xy{-1,-1}));
    vector<vector<bool>> two(h,vector<bool>(w,0));
    while (!q.empty()) {
        int x=q.top().x, y=q.top().y, d=q.top().d;
        q.pop();
        REP(k,4){
            int tox=x+dx[k], toy=y+dy[k];
            if(tox<0||tox>=h||toy<0||toy>=w)
                continue;
            if(s[tox][toy]=='#')
                continue;
            if(dis[tox][toy]>d+1){
                dis[tox][toy]=d+1;
                from[tox][toy]=xy{x,y};
                two[tox][toy]=two[x][y];
                q.push({tox,toy,d+1});
            }
            else if(dis[tox][toy]==d+1){
                two[tox][toy]=1;
            }
        }
    }
    if(dis[gx][gy]==INF)
        return -1;
    else if(two[gx][gy])
        return dis[gx][gy]*2;
    else{
        xy now={gx,gy};
        vector<vector<bool>> route(h,vector<bool>(w,0));
        while(now.x!=-1){
            route[now.x][now.y]=1;
            now=from[now.x][now.y];
        }
        REP(i,h)REP(j,w){
            if(route[i][j]){
                REP(k,4){
                    int tox=i+dx[k], toy=j+dy[k];
                    if(!route[tox][toy]&&s[tox][toy]=='.')
                        return dis[gx][gy]*2+2;
                }
            }
        }
        return -1;
    }
}

int main(){
    int sx, sy, gx, gy;
    cin >> h >> w >> sx >> sy >> gx >> gy;
    sx--, sy--, gx--, gy--;
    REP(i,h) cin >> s[i];
    cout << bfs(sx, sy, gx, gy) << endl;
    return 0;  
}