#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_set>
#include <vector>
using namespace std;
typedef long double ld;
typedef long long int ll;
typedef unsigned long long int ull;
typedef vector<int> vi;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
typedef vector<pair<int, int>> vpii;
typedef vector<pair<ll, ll>> vpll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<vc> vvc;
typedef vector<vs> vvs;
typedef vector<vll> vvll;
typedef map<int, int> mii;
typedef set<int> si;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i <= (n); ++i)
#define arep(i, v) for (auto i : v)
#define irep(it, stl) for (auto it = stl.begin(); it != stl.end(); it++)
#define drep(i, n) for (int i = (n)-1; i >= 0; --i)
#define fin(ans) cout << (ans) << '\n'
#define STLL(s) strtoll(s.c_str(), NULL, 10)
#define mp(p, q) make_pair(p, q)
#define pb(n) push_back(n)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define Sort(a) sort(a.begin(), a.end())
#define Rort(a) sort(a.rbegin(), a.rend())
#define MATHPI acos(-1)
#define fi first
#define se second
constexpr int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
template <class T>
inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline void dump(T& v) {
    irep(i, v) { cout << (*i) << ((i == --v.end()) ? '\n' : ' '); }
}
inline string getline() {
    string s;
    getline(cin, s);
    return s;
}
inline void yn(const bool b) { b ? fin("yes") : fin("no"); }
inline void Yn(const bool b) { b ? fin("Yes") : fin("No"); }
inline void YN(const bool b) { b ? fin("YES") : fin("NO"); }
struct io {
    io() {
        ios::sync_with_stdio(false);
        cin.tie(0);
    }
};
const int INF = INT_MAX;
constexpr ll LLINF = 1LL << 60;
constexpr ll MOD = 1000000007;
constexpr ld EPS = 1e-11;

/* --------------------   ここまでテンプレ   -------------------- */

class DIJKSTRA {
   public:
    int V;

    struct dk_edge {
        int to;
        ll cost;
    };

    typedef pair<ll, int> PI;  // firstは最短距離、secondは頂点の番号
    vector<vector<dk_edge>> G;
    vector<ll> d;      //これ答え。d[i]:=V[i]までの最短距離
    vector<int> prev;  //経路復元

    DIJKSTRA(int size) {
        V = size;
        G = vector<vector<dk_edge>>(V);
        prev = vector<int>(V, -1);
    }

    void add(int from, int to, ll cost) {
        dk_edge e = {to, cost};
        G[from].push_back(e);
    }

    void dijkstra(int s) {
        // greater<P>を指定することでfirstが小さい順に取り出せるようにする
        priority_queue<PI, vector<PI>, greater<PI>> que;
        d = vector<ll>(V, LLINF);
        d[s] = 0;
        que.push(PI(0, s));

        while (!que.empty()) {
            PI p = que.top();
            que.pop();
            int v = p.second;
            if (d[v] < p.first) continue;
            for (int i = 0; i < G[v].size(); i++) {
                dk_edge e = G[v][i];
                if (d[e.to] > d[v] + e.cost) {
                    d[e.to] = d[v] + e.cost;
                    prev[e.to] = v;
                    que.push(PI(d[e.to], e.to));
                }
            }
        }
    }
    vector<int> get_path(int t) {
        vector<int> path;
        for (; t != -1; t = prev[t]) {
            // tがsになるまでprev[t]をたどっていく
            path.push_back(t);
        }
        //このままだとt->sの順になっているので逆順にする
        reverse(path.begin(), path.end());
        return path;
    }
    void show(void) {
        for (int i = 0; i < d.size() - 1; i++) {
            cout << d[i] << " ";
        }
        cout << d[d.size() - 1] << endl;
    }
};
int main() {
    int h, w;
    cin >> h >> w;
    int sx, sy, gx, gy;
    cin >> sy >> sx >> gy >> gx;
    sx--;
    sy--;
    gx--;
    gy--;
    vs v(h);
    rep(i, h) cin >> v[i];
    DIJKSTRA dk(h * w);
    rep(i, h) {
        rep(j, w) {
            if (v[i][j] == '#') continue;
            for (int k = -2; k <= 2; k++) {
                for (int l = -2; l <= 2; l++) {
                    if (k == 0 && l == 0) continue;
                    int nx = j + k;
                    int ny = i + l;
                    if (nx < 0 || ny < 0 || nx >= w || ny >= h) continue;
                    if (v[ny][nx] == '#') continue;
                    auto p = mp(k, l);
                    int from = i * w + j;
                    int to = ny * w + nx;
                    if (p == mp(0, 1) || p == mp(1, 0) || p == mp(0, -1) ||
                        p == mp(-1, 0)) {
                        dk.add(from, to, 0);
                    } else {
                        dk.add(from, to, 1);
                    }
                }
            }
        }
    }
    dk.dijkstra(sy * w + sx);
    ll ans = dk.d[gy * w + gx];
    if (ans == LLINF)
        fin(-1);
    else
        fin(ans);
}


Measured memory_bytes: 172308