#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>
#include <climits>
#include <cstring>
#include <cassert>


using namespace std;
#define SZ(x) (int)(x.size())
#define REP(i, n) for(int i=0;i<n;++i)
#define FOR(i, a, b) for(int i=a;i<b;++i)
#define RREP(i, n) for(int i=n-1;i>=0;--i)
#define RFOR(i, a, b) for(int i=b-1;i>=a;--i)

#define all(x) begin(x),end(x)
#define dump(x) cerr<<#x<<" = "<<(x)<<endl
#define debug(x) cerr<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<< endl;

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using P = pair<int, int>;
const double eps = 1e-8;
const ll MOD = 1000000007;
const int INF = INT_MAX / 2;
const ll LINF = LLONG_MAX / 2;

template<class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}


template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> p) {
    os << p.first << ":" << p.second;
    return os;
}

template<class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    os << "[";
    REP(i, SZ(v)) {
        if (i) os << ", ";
        os << v[i];
    }
    return os << "]";
}

template<class T1, class T2>
ostream &operator<<(ostream &os, const map<T1, T2> &mp) {
    os << "[";
    for (auto it = mp.begin(); it != mp.end(); ++it) {
        if (it != mp.begin()) {
            os << ", ";
        }
        os << *it;
    }
    return os << "]";
}

// edit

template<typename T>
struct edge {
    int src, to;
    T cost;
};

template<typename T>
using Graph = vector<vector<edge<T>>>;

template<typename T>
std::vector<T> bfs01(const Graph<T> &g, int s) {
//    const T INF = numeric_limits<T>::max();
    std::vector<T> res(SZ(g), INF);
    deque<pair<T, int>> deq;
    res[s] = 0;
    deq.push_back({0, s});
    while (!deq.empty()) {
        auto elm = deq.front();
        deq.pop_front();
        T cost = elm.first;
        int now = elm.second;
        if (cost > res[now]) continue;

        for (auto &ne: g[now]) {
            int nxt = ne.to;
            if (res[nxt] > cost + ne.cost) {
                res[nxt] = cost + ne.cost;
                if (ne.cost == 0) {
                    deq.push_front({res[nxt], nxt});
                } else {
                    deq.push_back({res[nxt], nxt});
                }
            }
        }
    }

    return res;
}

void solve() {
    int H, W;
    cin >> H >> W;
    int ch, cw, dh, dw;
    cin >> ch >> cw >> dh >> dw;
    ch--, cw--, dh--, dw--;


    auto conv = [&](int h, int w) {
        return h * W + w;
    };

    auto inner = [&](int h, int w) {
        return h >= 0 && w >= 0 && h < H && w < W;
    };

    vector<string> S(H);
    REP(i, H) cin >> S[i];

//    UnionFind uf(H * W);
    Graph<int> g(H * W);

    for (int i = 0; i < H; ++i) {
        for (int j = 0; j < W; ++j) {
            for (int di = -2; di <= 2; ++di) {
                for (int dj = -2; dj <= 2; ++dj) {
                    int ni = i + di;
                    int nj = j + dj;
                    if (inner(ni, nj) && S[ni][nj] == '.') {
                        int from = conv(i, j);
                        int to = conv(ni, nj);
//                        uf.merge(from, to);
                        g[from].push_back(edge<int>{from, to, 1});
                    }
                }
            }

            int di[] = {-1, 0, 1, 0};
            int dj[] = {0, -1, 0, 1};
            for (int k = 0; k < 4; ++k) {
                int ni = i + di[k];
                int nj = j + dj[k];
                if (inner(ni, nj) && S[ni][nj] == '.') {
                    int from = conv(i, j);
                    int to = conv(ni, nj);
                    g[from].push_back(edge<int>{from, to, 0});
                }
            }
        }
    }

    int start = conv(ch, cw);
    int goal = conv(dh, dw);
    vector<int> dist = bfs01(g, start);
    if (dist[goal] == INF) {
        cout << -1 << endl;
        return;
    } else {
        cout << dist[goal] << endl;
    }


}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
//    std::ifstream in("input.txt");
//    std::cin.rdbuf(in.rdbuf());

    solve();


    return 0;
}


Measured memory_bytes: 280264