/* #region Head */

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

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U> using um = unordered_map<T, U>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqa = priority_queue<T, vc<T>, greater<T>>;
template <class T> using us = unordered_set<T>;

#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define PERM(c)                                                                                                        \
    sort(ALL(c));                                                                                                      \
    for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());

#define endl '\n'
#define sqrt sqrtl
#define floor floorl
#define log2 log2l

constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;

template <typename T> istream &operator>>(istream &is, vc<T> &vec) { // vector 入力
    for (T &x : vec) is >> x;
    return is;
}
template <typename T> ostream &operator<<(ostream &os, vc<T> &vec) { // vector 出力 (for dump)
    os << "{";
    REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "" : ", ");
    os << "}";
    return os;
}
template <typename T> ostream &operator>>(ostream &os, vc<T> &vec) { // vector 出力 (inline)
    REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "\n" : " ");
    return os;
}

template <typename T, typename U> istream &operator>>(istream &is, pair<T, U> &pair_var) { // pair 入力
    is >> pair_var.first >> pair_var.second;
    return is;
}
template <typename T, typename U> ostream &operator<<(ostream &os, pair<T, U> &pair_var) { // pair 出力
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

// map, um, set, us 出力
template <class T> ostream &out_iter(ostream &os, T &map_var) {
    os << "{";
    REPI(itr, map_var) {
        os << *itr;
        auto itrcp = itr;
        if (++itrcp != map_var.end()) os << ", ";
    }
    return os << "}";
}
template <typename T, typename U> ostream &operator<<(ostream &os, map<T, U> &map_var) { return out_iter(os, map_var); }
template <typename T, typename U> ostream &operator<<(ostream &os, um<T, U> &map_var) {
    os << "{";
    REPI(itr, map_var) {
        auto [key, value] = *itr;
        os << "(" << key << ", " << value << ")";
        auto itrcp = itr;
        if (++itrcp != map_var.end()) os << ", ";
    }
    os << "}";
    return os;
}
template <typename T> ostream &operator<<(ostream &os, set<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, us<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, pq<T> &pq_var) {
    pq<T> pq_cp(pq_var);
    os << "{";
    if (!pq_cp.empty()) {
        os << pq_cp.top(), pq_cp.pop();
        while (!pq_cp.empty()) os << ", " << pq_cp.top(), pq_cp.pop();
    }
    return os << "}";
}

// dump
#define DUMPOUT cerr
void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) DUMPOUT << ", ";
    dump_func(move(tail)...);
}

// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmax(T &xmax, const U &x, Comp comp = {}) {
    if (comp(xmax, x)) {
        xmax = x;
        return true;
    }
    return false;
}

// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmin(T &xmin, const U &x, Comp comp = {}) {
    if (comp(x, xmin)) {
        xmin = x;
        return true;
    }
    return false;
}

// ローカル用
#define DEBUG_

#ifdef DEBUG_
#define DEB
#define dump(...)                                                                                                      \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                                                                    \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl                                        \
            << "    ",                                                                                                 \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

struct AtCoderInitialize {
    static constexpr int IOS_PREC = 15;
    static constexpr bool AUTOFLUSH = false;
    AtCoderInitialize() {
        ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
        cout << fixed << setprecision(IOS_PREC);
        if (AUTOFLUSH) cout << unitbuf;
    }
} ATCODER_INITIALIZE;

void Yn(bool p) { cout << (p ? "Yes" : "No") << endl; }
void YN(bool p) { cout << (p ? "YES" : "NO") << endl; }

/* #endregion */

/* #region Graph */

// エッジ（本来エッジは双方向だが，ここでは単方向で管理）
template <class weight_t, class flow_t> struct Edge {
    ll src;          // エッジ始点となる頂点
    ll dst;          // エッジ終点となる頂点
    weight_t weight; // 重み
    flow_t cap;
    Edge() : src(0), dst(0), weight(0) {}
    Edge(ll src, ll dst, weight_t weight) : src(src), dst(dst), weight(weight) {}
    Edge(ll src, ll dst, weight_t weight, flow_t cap) : src(src), dst(dst), weight(weight), cap(cap) {}
    // Edge 標準出力
    friend ostream &operator<<(ostream &os, Edge &edge) {
        os << "(" << edge.src << " -> " << edge.dst << ", " << edge.weight << ")";
        return os;
    }
};
// 同じ頂点を始点とするエッジ集合
template <class weight_t, class flow_t> class Node : public vc<Edge<weight_t, flow_t>> {
  public:
    ll idx;
    Node() : vc<Edge<weight_t, flow_t>>() {}
    // void add(int a, int b, weight_t w, flow_t cap) { this->emplace_back(a, b, w, cap); };
};
// graph[i] := 頂点 i を始点とするエッジ集合
template <class weight_t, class flow_t> class Graph : public vc<Node<weight_t, flow_t>> {
  public:
    Graph() : vc<Node<weight_t, flow_t>>() {}
    Graph(int n) : vc<Node<weight_t, flow_t>>(n) { REP(i, 0, n)(*this)[i].idx = i; }
    // 単方向
    void add_arc(int a, int b, weight_t w = 1, flow_t cap = 1) { (*this)[a].emplace_back(a, b, w, cap); }
    // 双方向
    void add_edge(int a, int b, weight_t w = 1, flow_t cap = 1) { add_arc(a, b, w, cap), add_arc(b, a, w, cap); }
};
// using Array = vc<Weight>;
// using Matrix = vc<Array>;

/* #endregion */

// Problem
void solve() {
    ll h, w;
    cin >> h >> w;
    ll ch, cw, dh, dw;
    cin >> ch >> cw >> dh >> dw;
    --ch, --cw, --dh, --dw;
    vc<string> s(h);
    cin >> s;

    char wall = '#';
    const int dCol[4] = {1, 0, -1, 0};
    const int dRow[4] = {0, 1, 0, -1};
    vvll groupnums(h, vll(w, -1));
    // auto dfs = [&](auto &&dfs, ll num, ll curRow, ll curCol) -> void {
    //     if (groupnums[curRow][curCol] == num) return; // 訪問済み
    //     if (s[curRow][curCol] == wall) return;
    //     groupnums[curRow][curCol] = num;
    //     // for (Edge<ll, ll> &edge : graph[idx]) dfs(dfs, num, edge.dst);
    //     REP(dir, 0, 4) {
    //         ll nextRow = curRow + dRow[dir];
    //         ll nextCol = curCol + dCol[dir];
    //         if (nextRow < 0 || nextRow >= h || nextCol < 0 || nextCol >= w) continue;
    //         if (s[nextRow][nextCol] == wall) continue;
    //         // if (dist[nextRow][nextCol] != INF) continue; // 訪問済み（BFS）
    //         dfs(dfs, num, nextRow, nextCol);
    //     }
    // };
    ll num = 0;
    using node = pll;
    // REP(i, 0, h) REP(j, 0, w) if (groupnums[i][j] == -1 && s[i][j] != wall) dfs(dfs, num++, i, j);
    REP(sRow, 0, h) REP(sCol, 0, w) if (groupnums[sRow][sCol] == -1 && s[sRow][sCol] != wall) {
        groupnums[sRow][sCol] = num;
        queue<node> que;
        que.emplace(sRow, sCol);

        while (!que.empty()) {
            auto [curRow, curCol] = que.front();
            que.pop();
            // Dist curDist = dist[curRow][curCol];

            // cuerrent から辿れる頂点をすべて調べる
            REP(dir, 0, 4) {
                ll nextRow = curRow + dRow[dir];
                ll nextCol = curCol + dCol[dir];
                if (nextRow < 0 || nextRow >= h || nextCol < 0 || nextCol >= w) continue;
                if (s[nextRow][nextCol] == wall) continue;
                if (groupnums[nextRow][nextCol] != -1) continue; // 訪問済み（BFS）

                // Dist nextDist = curDist + 1;
                // if (chmin(dist[nextRow][nextCol], nextDist)) que.emplace(nextRow, nextCol); //
                // ↑この書き方はダイクストラっぽい
                groupnums[nextRow][nextCol] = num;
                que.emplace(nextRow, nextCol);
            }
        }
        num++;
    }
    // BFS 終了

    // dump(groupnums, num); // num に連結成分数が入っている
    if (groupnums[ch][cw] == groupnums[dh][dw]) {
        cout << 0 << endl;
        return;
    }
    // 1回以上ワープする

    // vc<vc<bool>> warpable(num, vc<bool>(num, false));
    // dump(groupnums);
    set<pll> arcs;

    // 左右の隣同士
    REP(i, 0, h) REP(j, 0, w) if (groupnums[i][j] != -1) {
        REPM(k, -2, 2) REPM(l, 0, 2) {
            ll ii = i + k;
            ll jj = j + l;
            if (ii < 0 || jj < 0 || ii >= h || jj >= w) continue;
            if (groupnums[ii][jj] == -1) continue;
            if (groupnums[ii][jj] == groupnums[i][j]) continue;
            // warpable[groupnums[i][j]][groupnums[ii][jj]] = true;
            // warpable[groupnums[ii][jj]][groupnums[i][j]] = true;
            arcs.emplace(groupnums[i][j], groupnums[ii][jj]);
            arcs.emplace(groupnums[ii][jj], groupnums[i][j]);
        }
        // REPM(k, -1, 1) REPM(l, -1, 1) {
        //     if (k == 0 && l == 0) continue;
        // }
    }
    // dump(warpable);
    // assert(false);

    Graph<ll, ll> graph(num);
    // REP(i, 0, num) REP(j, 0, num) if (warpable[i][j]) graph.add_arc(i, j);
    for (const pll &p : arcs) graph.add_arc(p.first, p.second);

    ll idx1 = groupnums[ch][cw]; // 始点として選ぶ頂点
    // if (SIZE(graph[idx1]) == 0) continue;

    using Weight = ll;
    using state = pair<Weight, ll>;                       // (始点からの最短経路長, ノード番号)
    priority_queue<state, vc<state>, greater<state>> que; // 昇順に並べ替え，小さい順に取り出す
    vc<Weight> dist(num, INF);
    dist[idx1] = 0;
    que.emplace(0, idx1);
    while (que.size()) {
        // tie(d, v) = que.top();
        state cur = que.top();
        que.pop();
        Weight d = cur.first;
        ll v = cur.second;

        if (dist[v] < d) continue;
        for (Edge<Weight, ll> edge : graph[v])
            if (chmin(dist[edge.dst], dist[v] + edge.weight)) que.emplace(dist[edge.dst], edge.dst);
    }
    // ここまでで， idx1 を始点として各頂点までの距離が dist に入った
    // ただし，到達不可能な頂点は距離が INF になっているので，
    // chmax(ret, *max_element(ALL(dist))); は不可

    if (dist[groupnums[dh][dw]] == INF) {
        cout << -1 << endl;
    } else {
        cout << dist[groupnums[dh][dw]] << endl;
    }
}

// entry point
int main() {
    solve();
    return 0;
}


Measured memory_bytes: 58568