#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using vl = vector<ll>;
template<class T> using vc = vector<T>;
template<class T> using vvc = vector<vector<T>>;

#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define repr(i, n) for (ll i = (n)-1; i >= 0; i--)
#define repe(i, l, r) for (ll i = (l); i < (r); i++)
#define reper(i, l, r) for (ll i = (r)-1; i >= (l); i--)
#define repa(i,n) for (auto& i: n)

template<class T> inline bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> inline bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
void init() {cin.tie(0);ios::sync_with_stdio(false);cout << fixed << setprecision(15);}

#ifdef DEBUG
template <class T, class N> void verr(const T& a, const N& n) { rep(i, n) cerr << a[i] << " "; cerr << "\n" << flush; }
ll dbgt = 1; void err() { cerr << "passed " << dbgt++ << "\n" << flush; }
template<class H, class... T> void err(H&& h,T&&... t){ cerr<< h << (sizeof...(t)?" ":"\n") << flush; if(sizeof...(t)>0) err(forward<T>(t)...); }
#endif

const ll INF = 4e18;
const ld EPS = 1e-11;
const ld PI = acos(-1.0L);
const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
//--------------------------------------------------------------------------------//
struct UnionFind {
private:
    vector<int> par;
    vector<int> count;
    vector<int> rank;
public:
    UnionFind(int N) {
        count.assign(N, 1);
        rank.assign(N, 0);
        par.assign(N, 0);
        rep(i, N) par[i] = i;
    }

    int root(int x) {
        if (par[x] == x)
            return x;
        else {
            par[x] = root(par[x]);
            return par[x];
        }
    }

    void unite(int x, int y) {
        x = root(x), y = root(y);
        if (x == y) return;
        if (rank[x] < rank[y])
            swap(x, y);
        else if (rank[x] == rank[y])
            rank[y]++;
        par[y] = x;
        count[x] += count[y];
        return;
    }

    int size(int x) {
        return count[root(x)];
    }

    bool issame(int x, int y) {
        return root(x) == root(y);
    }
};
using UF = struct UnionFind;

template <typename T>
struct dijkstra{
    using P = pair<T, ll>;
    const T inf = numeric_limits<T>::max();
    vector<vector<pair<ll,T>>> G;
    vector<ll> beforev;
    vector<T> dist;
    ll N, start;
    priority_queue<P, vector<P>, greater<P>> pq;

    dijkstra(ll n) : N(n) {
        G.resize(n), beforev.assign(n, -1), dist.assign(n, inf);
    }

    void add_edge(ll u, ll v, T cost){
        G[u].emplace_back(v, cost);
    }

    void init(ll s = 0){
        start = s;
        fill(beforev.begin(), beforev.end(), -1), fill(dist.begin(), dist.end(), inf);
        dist[start] = 0, pq.emplace(0, start);
        
        while(!pq.empty()){
            T c; ll from;
            tie(c, from) = pq.top(), pq.pop();
            if (dist[from] < c) continue;
            for(auto& e: G[from]){
                ll to; T cost;
                tie(to, cost) = e;
                if(dist[to]>dist[from]+cost){
                    dist[to] = dist[from] + cost;
                    beforev[to] = from;
                    pq.emplace(dist[to], to);
                }
            }
        }
    }

    vector<ll> get_route(ll goal){
        vector<ll> route;
        ll now = goal;
        while(now!=-1){
            route.emplace_back(now);
            now = beforev[now];
        }
        reverse(route.begin(), route.end());
        return route;
    }
};

int main() {
    init();
    ll H, W, ch, cw, dh, dw;
    cin >> H >> W >> ch >> cw >> dh >> dw;
    ch--, cw--, dh--, dw--;

    vc<string> S(H);
    rep(i, H) cin >> S[i];

    UF uf(H * W);

    vl ddi = {0, 0, 1, -1}, ddj = {1, -1, 0, 0};
    rep(i, H) rep(j, W) {
        if (S[i][j] == '#') continue;

        rep(d, 4) {
            ll ti = i + ddi[d], tj = j + ddj[d];
            if (ti < 0 or ti >= H or tj < 0 or tj >= W) continue;
            if (S[ti][tj] == '#') continue;
            uf.unite(i * W + j, ti * W + tj);
        }
    }

    if (uf.root(ch * W + cw) == uf.root(dh * W + dw)) {
        cout << 0 << endl;
        return 0;
    }

    dijkstra<ll> G(H * W);
    map<pair<ll,ll>, bool> mp;
    
    rep(i, H) rep(j, W) {
        if (S[i][j] == '#') continue;
        rep(di, 5) rep(dj, 5) {
            ll ti = i + di - 2, tj = j + dj - 2;
            if (ti < 0 or ti >= H or tj < 0 or tj >= W) continue;
            if (S[ti][tj] == '#') continue;

            ll p1 = uf.root(i * W + j), p2 = uf.root(ti * W + tj);
            if (p1 == p2) continue;

            if (!mp[{p1, p2}]) {
                mp[{p1, p2}] = mp[{p2, p1}] = true;
                G.add_edge(p1, p2, 1), G.add_edge(p2, p1, 1);
            }
        }
    }

    G.init(uf.root(ch * W + cw));

    ll ans = G.dist[uf.root(dh * W + dw)];
    // err(ans, uf.par[ch * W + cw], uf.par[dh * W + dw]);
    cout << (ans > INF ? -1 : ans) << endl;
}


Measured memory_bytes: 89208