#pragma region Headers
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cwchar>
#include <cwctype>

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <codecvt>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif
#pragma endregion

using namespace std;
#pragma region Macros
#define CHOOSE(a) CHOOSE2 a
#define CHOOSE2(a0, a1, a2, a3, a4, x, ...) x
#define debug_1(x1) cout << #x1 << ": " << x1 << endl
#define debug_2(x1, x2) cout << #x1 << ": " << x1 << ", " #x2 << ": " << x2 << endl
#define debug_3(x1, x2, x3) cout << #x1 << ": " << x1 << ", " #x2 << ": " << x2 << ", " #x3 << ": " << x3 << endl
#define debug_4(x1, x2, x3, x4) cout << #x1 << ": " << x1 << ", " #x2 << ": " << x2 << ", " #x3 << ": " << x3 << ", " #x4 << ": " << x4 << endl
#define debug_5(x1, x2, x3, x4, x5) cout << #x1 << ": " << x1 << ", " #x2 << ": " << x2 << ", " #x3 << ": " << x3 << ", " #x4 << ": " << x4 << ", " #x5 << ": " << x5 << endl
#ifdef _DEBUG
#define debug(...)                                                        \
    CHOOSE((__VA_ARGS__, debug_5, debug_4, debug_3, debug_2, debug_1, ~)) \
    (__VA_ARGS__)
#else
#define debug(...)
#endif
#pragma region end

#pragma region Libraries
template <typename T>
string to_string(T o)
{
    stringstream s;
    s << o;
    return s.str();
}

template <typename T>
string to_string(vector<T> v)
{
    stringstream s;
    s << "[";
    for (auto i = 0; i < v.size(); i++)
    {
        s << to_string(v.at(i));
        if (i != v.size() - 1)
        {
            s << ", ";
        }
    }
    s << "]";
    return s.str();
}

template <typename T>
ostream &operator<<(ostream &o, const vector<T> &obj)
{
    o << to_string(obj);
    return o;
}

template <typename T>
string to_string(vector<vector<T>> m)
{
    stringstream s;
    s << "[" << endl;
    for (auto i = 0; i < m.size(); i++)
    {
        auto v = m[i];
        s << "  "
          << "#" << i << ":"
          << " " << to_string(v);
        s << ", " << endl;
    }
    s << "]";
    return s.str();
}

template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &obj)
{
    o << to_string(obj);
    return o;
}

template <typename K, typename V>
string to_string(pair<K, V> p)
{
    stringstream s;
    s << "pair(" << to_string(p.first) << ", " << to_string(p.second) << ")";
    return s.str();
}

template <typename K, typename V>
ostream &operator<<(ostream &o, const pair<K, V> &obj)
{
    o << to_string(obj);
    return o;
}

template <typename K, typename V>
string to_string(map<K, V> m)
{
    stringstream s;
    s << "{" << endl;
    for (const auto &p : m)
    {
        s << "  " << to_string(p.first) << ": " << to_string(p.second) << "," << endl;
    }
    s << "}";
    return s.str();
}

template <typename K, typename V>
ostream &operator<<(ostream &o, const map<K, V> &obj)
{
    o << to_string(obj);
    return o;
}

template <typename T>
string to_string(set<T> ss)
{
    stringstream s;
    s << "set"
      << "{";
    for (auto itr = ss.begin(); itr != ss.end(); itr++)
    {
        s << to_string(*itr);
        if (next(itr, 1) != ss.end())
        {
            s << ", ";
        }
    }
    s << "}";
    return s.str();
}

template <typename T>
ostream &operator<<(ostream &o, const set<T> &obj)
{
    o << to_string(obj);
    return o;
}

template <typename T>
string to_string(queue<T> q)
{
    auto temp = queue<T>{};
    stringstream s;
    s << "queue{";
    while (!q.empty())
    {
        auto top = q.front();
        s << to_string(top) << ", ";
        q.pop();
        temp.push(top);
    }
    s << "}";

    while (!temp.empty())
    {
        auto top = temp.front();
        temp.pop();
        q.push(top);
    }

    return s.str();
}

template <typename T>
ostream &operator<<(ostream &o, const queue<T> &obj)
{
    o << to_string(obj);
    return o;
}
#pragma endregion

typedef long long ll;

int main()
{
    cin.tie(0);
    ll H, W;
    char M[1001][1001];
    ll CH, CW, DH, DW;

    cin >> H >> W;
    cin >> CH >> CW;
    cin >> DH >> DW;
    const int initial = 9999999;
    vector<vector<int>> costs(H, vector<int>(W, initial));

    CH--;
    CW--;
    DH--;
    DW--;

    for (auto i = 0; i < H; i++)
    {
        for (auto j = 0; j < W; j++)
        {
            char w;
            cin >> w;
            M[i][j] = w;
        }
    }

    // 壁の中にいたら困る
    if (M[CH][CW] == '#')
    {
        throw runtime_error("in the wall");
    }
    // 自分のマスから他のマスにジャンプできるか.
    queue<pair<ll, ll>> q;
    q.push(make_pair(CH, CW));

    vector<ll> move_h = {0, 1, -1, 0};
    vector<ll> move_w = {1, 0, 0, -1};

    costs[CH][CW] = 0;

    while (costs[DH][DW] == initial && !q.empty())
    {
        auto p = q.front();
        q.pop();

        queue<pair<ll, ll>> qq;
        qq.push(p);
        set<pair<ll, ll>> visited_at_cycle;
        visited_at_cycle.insert(p);

        while (!qq.empty())
        {
            auto pp = qq.front();
            qq.pop();
            int cur_cost = costs[pp.first][pp.second];

            for (auto i = 0; i < 4; i++)
            {
                auto hh = move_h[i];
                auto ww = move_w[i];

                ll hhh = pp.first + hh;
                ll www = pp.second + ww;

                if (hhh >= 0 && www >= 0 && hhh < H && www < W)
                {
                    if (M[hhh][www] == '.')
                    {
                        int next_cost = costs[hhh][www];
                        auto next_pair = make_pair(hhh, www);
                        if ((visited_at_cycle.count(next_pair) == 0))
                        {
                            debug(next_pair, min(costs[hhh][www], costs[p.first][p.second]));
                            costs[hhh][www] = min(next_cost, cur_cost);
                            qq.push(next_pair);
                            visited_at_cycle.insert(next_pair);
                        }
                    }
                }
            }
        }

        for (auto pp : visited_at_cycle)
        {
            debug("jump", pp);
            int cur_cost = costs[pp.first][pp.second];
            for (auto i = -2; i <= 2; i++)
            {
                for (auto j = -2; j <= 2; j++)
                {
                    ll hhh = pp.first + i;
                    ll www = pp.second + j;

                    if (hhh >= 0 && www >= 0 && hhh < H && www < W)
                    {
                        if (M[hhh][www] == '.')
                        {
                            int next_cost = costs[hhh][www];
                            if (next_cost == initial || next_cost > cur_cost + 1)
                            {
                                debug(make_pair(hhh, www), min(cur_cost + 1, next_cost));
                                costs[hhh][www] = min(cur_cost + 1, next_cost);
                                q.push(make_pair(hhh, www));
                            }
                        }
                    }
                }
            }
        }
    }

    if (costs[DH][DW] == initial)
    {
        cout << -1 << endl;
    }
    else
    {
        cout << costs[DH][DW] << endl;
    }

    debug(costs);

    return 0;
}


Measured memory_bytes: 8076