#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())
#define endl "\n"
template<class T> void chmax(T &a, const T b){ a = max(a, b); }
template<class T> void chmin(T &a, const T b){ a = min(a, b); }

template<class T>
struct Dijkstra {
    const T inf = numeric_limits<T>::max() / 2 - 1;
    vector<T> dist;
    vector<int> path;
    
    Dijkstra() {}
    Dijkstra(int n) {
        graph.resize(n);
        dist.resize(n);
        prev.resize(n);
    }
    
    void add_edge(int from, int to, T cost) {
        graph[from].emplace_back(to, cost);
    }
    
    void get_distance(int from) {
        priority_queue<pair<T, int>, vector<pair<T, int>>, greater<pair<T, int>>> pq;
        fill(dist.begin(), dist.end(), inf);
        fill(prev.begin(), prev.end(), -1);
        dist[from] = 0;
        pq.push(make_pair(0, from));
        while(!pq.empty()) {
            pair<T, int> p = pq.top(); pq.pop();
            if (dist[p.second] < p.first) continue;
            for (auto e : graph[p.second]) {
                if (dist[e.first] > (dist[p.second] + e.second)) {
                    dist[e.first] = dist[p.second] + e.second;
                    prev[e.first] = p.second;
                    pq.push(make_pair(dist[e.first], e.first));
                }
            }
        }
    }
    
    void get_path(int to) {
        path = vector<int>(0);
        for (; to != -1; to = prev[to]) {
            path.push_back(to);
        }
        reverse(path.begin(), path.end());
    }
    
private:
    vector<vector<pair<int, T>>> graph;
    vector<T> prev;
};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    const ll dir[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
    const ll inf = LONG_LONG_MAX / 2 - 1;
    ll h, w;
    cin >> h >> w;
    ll ch, cw, dh, dw;
    cin >> ch >> cw >> dh >> dw;
    ch--; cw--; dh--; dw--;
    vector<string> s(h);
    rep(i, h) cin >> s[i];
    Dijkstra<ll> di(h * w);
    rep(y, h) {
        rep(x, w) {
            rep(i, 4) {
                ll nx = x + dir[i][0];
                ll ny = y + dir[i][1];
                if ((nx < 0) || (nx >= w) || (ny < 0) || (ny >= h)) continue;
                if (s[ny][nx] != '.') continue;
                di.add_edge(y * w + x, ny * w + nx, 0);
            }
            reps(dy, -2, 3) {
                reps(dx, -2, 3) {
                    if ((dy == 0) && (dx == 0)) continue;
                    ll nx = x + dx;
                    ll ny = y + dy;
                    if ((nx < 0) || (nx >= w) || (ny < 0) || (ny >= h)) continue;
                    if (s[ny][nx] != '.') continue;
                    di.add_edge(y * w + x, ny * w + nx, 1);
                }
            }
        }
    }
    di.get_distance(ch * w + cw);
    if (di.dist[dh * w + dw] == inf) {
        cout << -1 << endl;
    }
    else {
        cout << di.dist[dh * w + dw] << endl;
    }
    return 0;
}


Measured memory_bytes: 354964