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

using point = pair<int, int>;
const vector<int> dx{1, 0, -1, 0}, dy{0, 1, 0, -1};

int main() {
    constexpr int inf = 1e9;
    int h, w, ra, ca, rb, cb;
    cin >> h >> w >> ra >> ca >> rb >> cb;
    ra--; ca--; rb--; cb--;
    vector<string> s(h);
    for (int i = 0; i < h; i++) {
        cin >> s.at(i);
    }
    vector d(h, vector(w, inf)), db(h, vector(w, inf)), dloop(h, vector(w, inf));
    queue<point> q;
    d.at(ra).at(ca) = 0;
    q.emplace(ra, ca);
    while (not q.empty()) {
        auto [x, y] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int newx = x + dx.at(i), newy = y + dy.at(i);
            if (s.at(newx).at(newy) == '#') continue;            
            if (d.at(newx).at(newy) != inf) continue;
            d.at(newx).at(newy) = d.at(x).at(y) + 1;
            q.emplace(newx, newy);
        }
    }
    const int dist = d.at(rb).at(cb);
    if (dist == inf) {
        cout << -1 << endl;
        return 0;
    }
    db.at(rb).at(cb) = 0;
    q.emplace(rb, cb);
    while (not q.empty()) {
        auto [x, y] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int newx = x + dx.at(i), newy = y + dy.at(i);
            if (s.at(newx).at(newy) == '#') continue;            
            if (db.at(newx).at(newy) != inf) continue;
            db.at(newx).at(newy) = db.at(x).at(y) + 1;
            q.emplace(newx, newy);
        }
    }
    vector<vector<int>> v(2 * h * w), v_back(h * w), v_front(h * w);
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            if (d.at(i).at(j) == inf or db.at(i).at(j) == inf) continue;
            int d_total = d.at(i).at(j) + db.at(i).at(j);
            if (abs(d.at(i).at(j) - db.at(i).at(j)) < dist) {
                v.at(d.at(i).at(j) - db.at(i).at(j) + h * w).push_back(d_total);
            } else if (d.at(i).at(j) - db.at(i).at(j) > 0) {
                v_back.at(d.at(i).at(j)).push_back(d_total);
            } else {
                v_front.at(db.at(i).at(j)).push_back(d_total);
            }
        }
    }
    int ans = inf;
    for (int i = 0; i < 2 * h * w; i++) {
        sort(v.at(i).begin(), v.at(i).end());
        if (v.at(i).size() >= 2) {
            ans = min(ans, v.at(i).at(0) + v.at(i).at(1));
        }
        if (i >= h * w) continue;
        sort(v_back.at(i).begin(), v_back.at(i).end());
        if (v_back.at(i).size() >= 2) {
            ans = min(ans, v_back.at(i).at(0) + v_back.at(i).at(1));
        }
        sort(v_front.at(i).begin(), v_front.at(i).end());
        if (v_front.at(i).size() >= 2) {
            ans = min(ans, v_front.at(i).at(0) + v_front.at(i).at(1));
        }
    }
    int x_erase = rb, y_erase = cb, d_erase = dist;
    while (d_erase) {
        s.at(x_erase).at(y_erase) = '#';
        for (int i = 0; i < 4; i++) {
            int newx = x_erase + dx.at(i), newy = y_erase + dy.at(i);
            if (s.at(newx).at(newy) == '#') continue;
            if (d.at(newx).at(newy) >= d_erase) continue;
            x_erase = newx;
            y_erase = newy;
            d_erase--;
            break;
        }
    }
    s.at(rb).at(cb) = '.';
    dloop.at(ra).at(ca) = 0;
    q.emplace(ra, ca);
    while (not q.empty()) {
        auto [x, y] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int newx = x + dx.at(i), newy = y + dy.at(i);
            if (s.at(newx).at(newy) == '#') continue;            
            if (dloop.at(newx).at(newy) != inf) continue;
            if (x == ra and y == ca and newx == rb and newy == cb) continue;
            dloop.at(newx).at(newy) = dloop.at(x).at(y) + 1;
            q.emplace(newx, newy);
        }
    }
    ans = min(ans, dist + dloop.at(rb).at(cb));
    if (ans == inf) {
        cout << -1 << endl;
    } else {
        cout << ans << endl;
    }
}