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


#define li          long long int
#define uli         unsigned long long int
#define rep(i,to)   for(li i=0;i<((li)(to));i++)
#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)
#define pb          push_back
#define sz(v)       ((li)(v).size())
#define bgn(v)      ((v).begin())
#define eend(v)     ((v).end())
#define allof(v)    (v).begin(), (v).end()
#define dodp(v,n)       memset(v,(li)n,sizeof(v))
#define bit(n)      (1ll<<(li)(n))
#define mp(a,b)     make_pair(a,b)
#define rin rep(i,n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 1000000007
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1


#define idp if(DBGP)
#define F first
#define S second
#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl
#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl
#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl
#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl
#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl
#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl
#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl
#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl
#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl
#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)
#define p2p(x)      idp p2((x).F, (x).S)
#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}
#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}
#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}
#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}

#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]
#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}

typedef pair<li, li> PI;

li h, w;
PI c, d;

string board[3030];

//li dy[] = { -1, 1, 0, 0};
//li dx[] = {0, 0, -1, 1};

int main() {
    cin >> h >> w;
    cin >> c.F >> c.S;
    c.F--;
    c.S--;
    cin >> d.F >> d.S;
    d.F--;
    d.S--;
    rep(i, h) {
        cin >> board[i];
    }

    priority_queue<pair<li, PI>> pq;
    pq.push({0, c});
    map<PI, li> visited;
    while (!pq.empty()) {
        li now_cost = -pq.top().F;
        PI now = pq.top().S;
        pq.pop();
        if (visited.count(now) > 0) {
            continue;
        }
        visited[now] = now_cost;
        if (now == d) {
            cout << now_cost << endl;
            return 0;
        }
        repp(dy, -2, 3) {
            repp(dx, -2, 3) {
                PI next = {now.F + dy, now.S + dx};
                if (min(next.F, next.S) < 0 || next.F >= h || next.S >= w) {
                    continue;
                }
                li d = abs(next.F - now.F) + abs(next.S - now.S);
                if (d == 0) {
                    continue;
                }
                if (board[next.F][next.S] == '#') {
                    continue;
                }
                if (d == 1) {
                    pq.push({ -now_cost, next});
                } else {
                    pq.push({ -now_cost - 1, next});
                }
            }
        }
    }
    puts("-1");

    return 0;
}


Measured memory_bytes: 33512