#ifdef LOCAL
//#define _GLIBCXX_DEBUG
#endif
//#pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<int, int> Pi;
typedef vector<ll> Vec;
typedef vector<int> Vi;
typedef vector<string> Vs;
typedef vector<char> Vc;
typedef vector<P> VP;
typedef vector<vector<ll>> VV;
typedef vector<vector<int>> VVi;
typedef vector<vector<char>> VVc;
typedef vector<vector<vector<ll>>> VVV;
typedef vector<vector<vector<vector<ll>>>> VVVV;

#define REP(i, a, b) for(ll i=(a); i<(b); i++)
#define PER(i, a, b) for(ll i=(a); i>=(b); i--)
#define rep(i, n) REP(i, 0, n)
#define per(i, n) PER(i, n, 0)
const ll INF=1e18+18;
const ll MOD=1000000007;
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl;
#define YES(n) cout << ((n) ? "YES" : "NO") << endl;
#define ALL(v) v.begin(), v.end()
#define rALL(v) v.rbegin(), v.rend()
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a,b)
#define Each(a,b) for(auto &a :b)
#define rEach(i, mp) for (auto i = mp.rbegin(); i != mp.rend(); ++i)
#ifdef LOCAL
#define dbg(x_) cerr << #x_ << ":" << x_ << endl;
#define dbgmap(mp) cerr << #mp << ":"<<endl; for (auto i = mp.begin(); i != mp.end(); ++i) { cerr << i->first <<":"<<i->second << endl;}
#define dbgset(st) cerr << #st << ":"<<endl; for (auto i = st.begin(); i != st.end(); ++i) { cerr << *i <<" ";}cerr<<endl;
#define dbgarr(n,m,arr) rep(i,n){rep(j,m){cerr<<arr[i][j]<<" ";}cerr<<endl;}
#define dbgdp(n,arr) rep(i,n){cerr<<arr[i]<<" ";}cerr<<endl;
#else
#define dbg(...)
#define dbgmap(...)
#define dbgset(...)
#define dbgarr(...)
#define dbgdp(...)
#endif
#define out(a) cout<<a<<endl
#define out2(a,b) cout<<a<<" "<<b<<endl
#define vout(v) rep(i,v.size()){cout<<v[i]<<" ";}cout<<endl
#define Uniq(v) v.erase(unique(v.begin(), v.end()), v.end())
#define fi first
#define se second

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }

template<typename T1, typename T2>
ostream &operator<<(ostream &s, const pair<T1, T2> &p) { return s<<"("<<p.first<<", "<<p.second<<")"; }

template<typename T>istream& operator>>(istream&i,vector<T>&v)
{rep(j,v.size())i>>v[j];return i;}

// vector
template<typename T>
ostream &operator<<(ostream &s, const vector<T> &v) {
    int len=v.size();
    for(int i=0; i<len; ++i) {
        s<<v[i];
        if(i<len-1) s<<"	";
    }
    return s;
}

// 2 dimentional vector
template<typename T>
ostream &operator<<(ostream &s, const vector<vector<T> > &vv) {
    int len=vv.size();
    for(int i=0; i<len; ++i) {
        s<<vv[i]<<endl;
    }
    return s;
}

void dijkstra(vector<VP> &g, ll start, Vec &dist) {
    priority_queue<P, vector<P>, function<bool(P, P)>> q([](P a, P b)->ll {
        return a.second > b.second;
    });
    dist[start] = 0;
    q.push(mp(start, 0));
    while (!q.empty()) {
        P now = q.top();
        q.pop();
        Each(nxt, g[now.fi]) {
            if(chmin(dist[nxt.fi], now.se+nxt.se)) {
                q.push(mp(nxt.fi, dist[nxt.fi]));
            }
        }
    }
}


int solve(){
    ll h,w;
    cin>>h>>w;
    ll sh,sw;
    cin>>sh>>sw;
    sh--;sw--;
    ll gh,gw;
    cin>>gh>>gw;
    gh--;gw--;
    vector<vector<char>> g(h,vector<char>(w));

    auto idx = [&](ll y, ll x) { return y*w+x; };
    rep(i,h){
        string s;
        cin>>s;
        rep(j,w){
            g[i][j] = s[j];
        }
    }
    dbg(g);
    auto in = [&](ll y, ll x) {
        return y >= 0 && y < h && x >= 0 && x < w;
    };

    vector<VP> G(h*w);
    Vec dx = {1,0,-1,0,1,-1,1,-1};
    Vec dy = {0,1,0,-1,1,1,-1,-1};
    rep(i,h){
        rep(j,w){
            ll now = idx(i,j);
            if(g[i][j]=='#'){
                continue;
            }
            rep(k,4){
                ll ni = i+dy[k];
                ll nj = j+dx[k];
                if(!in(ni,nj))continue;
                if(g[ni][nj]=='#')continue;
                ll nx = idx(ni,nj);
                G[now].emplace_back(nx,0);
                G[nx].emplace_back(now,0);
            }

            rep(dy,5){
                rep(dx,5){
                    ll ni = i+dy-2;
                    ll nj = j+dx-2;
                    if(!in(ni,nj))continue;
                    if(g[ni][nj]=='#')continue;
                    ll nx = idx(ni,nj);
                    G[now].emplace_back(nx,1);
                    G[nx].emplace_back(now,1);
                }
            }
        }
    }

    //dbg(G);
    ll start = idx(sh,sw);
    ll goal = idx(gh,gw);
    Vec dist(h*w,INF);

    dijkstra(G,start,dist);
    dbg(dist);

    if(dist[goal]==INF){
        out(-1);
    }else{
        out(dist[goal]);
    }

    return  0;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout<<std::setprecision(10);
//    ll T;
//    cin>>T;
//    while(T--)
    solve();
}


Measured memory_bytes: 367488