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

int H, W, ax, ay, bx, by;
vector<string> S;


int main() {
    cin >> H >> W >> ax >> ay >> bx >> by;
    ax--;
    ay--;
    bx--;
    by--;
    S.resize(H);
    for (int i = 0; i < H; i++) {
        cin >> S[i];
        for (auto& c : S[i])
            if (c == '#')
                c = 1;
            else
                c = 0;
    }

    const int dx[] = {1, 0, -1, 0};
    const int dy[] = {0, -1, 0, 1};

    queue<pair<int, pair<int, int>>> que;
    que.push(make_pair(0, make_pair(ax, ay)));
    vector<vector<int>> dist(H, vector<int>(W, -1));
    dist[ax][ay] = 0;
    que.push(make_pair(0, make_pair(ax, ay)));
    while (!que.empty()) {
        auto p = que.front();
        que.pop();
        int d = p.first, now_x = p.second.first, now_y = p.second.second;
        if (now_x == bx && now_y == by)
            continue;
        for (int i = 0; i < 4; i++) {
            int nxt_x = now_x + dx[i], nxt_y = now_y + dy[i];
            if (S[nxt_x][nxt_y] == 1) {
                continue;
            }
            if (dist[nxt_x][nxt_y] == -1) {
                dist[nxt_x][nxt_y] = d + 1;
                que.push(make_pair(d + 1, make_pair(nxt_x, nxt_y)));
            }
        }
    }

    if (dist[bx][by] == -1) {
        cout << -1 << endl;
        return 0;
    }

    bool flag1 = false, flag2 = false;
    int now_x = bx, now_y = by, now_dist = dist[bx][by];
    while (!(now_x == ax && now_y == ay)) {
        int cnt1 = 0, cnt2 = 0, tmp_x, tmp_y;
        for (int i = 0; i < 4; i++) {
            int nxt_x = now_x + dx[i], nxt_y = now_y + dy[i];
            if (dist[nxt_x][nxt_y] == now_dist - 1) {
                cnt1++;
                tmp_x = nxt_x;
                tmp_y = nxt_y;
            }
            if (S[nxt_x][nxt_y] == 0)
                cnt2++;
        }
        if (cnt1 >= 2)
            flag1 = true;
        if (now_dist != dist[bx][by])
            if (cnt2 >= 3)
                flag2 = true;

        now_x = tmp_x;
        now_y = tmp_y;
        now_dist--;
    }
    if (flag1) {
        cout << dist[bx][by] * 2 << endl;
    } else if (flag2) {
        cout << dist[bx][by] * 2 + 2 << endl;
    } else {
        int ans = -1;
        vector<int> d;
        for (int i = 0; i < 4; i++) {
            int tmp = dist[bx + dx[i]][by + dy[i]];
            if (tmp != -1)
                d.emplace_back(tmp);
        }
        sort(d.begin(), d.end());
        if (d.size() >= 2) {
            ans = d[0] + d[1] + 2;
        }
        cout << ans << endl;
    }
}