#include <cstring>
#include <tuple>
#include <algorithm>
#include <queue>
#include <vector>
#include <iostream>
using namespace std;
template<typename Callback>
inline void for_nbd4(int x, int y, int lx, int ux, int ly, int uy, Callback f) {
    constexpr pair<int, int> dxdy[] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
    for (auto [dx, dy] : dxdy) {
        const int u = x + dx, v = y + dy;
        if (lx <= u && u < ux && ly <= v && v < uy) f(u, v);
    }
}
template<typename Callback>
inline void for_nbd4(int x, int y, int X, int Y, Callback f) {
    for_nbd4(x, y, 0, X, 0, Y, f);
}

template<typename T, typename Callback>
inline T sum_nbd4(int x, int y, int lx, int ux, int ly, int uy, Callback f) {
    constexpr pair<int, int> dxdy[] = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
    T result{};
    for (auto [dx, dy] : dxdy) {
        const int u = x + dx, v = y + dy;
        if (lx <= u && u < ux && ly <= v && v < uy) result += f(u, v);
    }
    return result;
}
template<typename T, typename Callback>
inline T sum_nbd4(int x, int y, int X, int Y, Callback f) {
    return sum_nbd4<T, Callback>(x, y, 0, X, 0, Y, f);
}

int main() {
    int h, w, sx, sy, gx, gy; cin >> h >> w >> sx >> sy >> gx >> gy;
    sx--; sy--; gx--; gy--;
    vector<string> S(h);
    for (int i = 0; i < h; i++) cin >> S[i];
    int dist[h][w], count[h][w];
    pair<int, int> from[h][w];
    constexpr int INF = 1<<30;
    priority_queue<tuple<int, int, int> > pq;
    for (int i = 0; i < h; i++)
        for (int j = 0; j < w; j++)
            if (i == sx && j == sy) {
                dist[i][j] = 0;
                count[i][j] = 1;
                from[i][j] = {-1, -1};
                pq.push({0, i, j});
            } else {
                dist[i][j] = INF;
                count[i][j] = 0;
            }
    while (!pq.empty()) {
        auto [d, x, y] = pq.top();
        pq.pop();
        d = -d;
        if (dist[x][y] < d) continue;
        for_nbd4(x, y, h, w, [d=d, x=x, y=y, &S, &dist, &pq, &count, &from](int u, int v) {
                if (S[u][v] == '#') return;
                if (dist[u][v] > dist[x][y] + 1) {
                    dist[u][v] = dist[x][y] + 1;
                    count[u][v] = count[x][y];
                    from[u][v] = {x, y};
                    pq.push({-dist[u][v], u, v});
                } else if (dist[u][v] == dist[x][y] + 1) {
                    count[u][v] += count[x][y];
                }
            });
    }
    // for (int i = 0; i < h; i++)
    //     for (int j = 0; j < w; j++)
    //         cerr << i << ' ' << j << ' ' << dist[i][j] << ' ' << count[i][j] << endl;
    if (count[gx][gy] == 0) cout << -1 << endl;
    else if (count[gx][gy] > 1) cout << 2 * dist[gx][gy] << endl;
    else {
        int x = gx, y = gy;
        for (;;) {
            tie(x, y) = from[x][y];
            if (x == sx && y == sy) break;
            if (sum_nbd4<int>(x, y, h, w, [&](int u, int v) {return int(S[u][v] == '.');}) > 2)
            {
                cout << 2 * dist[gx][gy] + 2 << endl;
                return 0;
            }
            S[x][y] = '#';
        }

        const int d0 = dist[gx][y];
        for (int i = 0; i < h; i++)
            for (int j = 0; j < w; j++)
                dist[i][j] = (i == sx && j == sy) ? 0 : INF;
        pq.push({0, sx, sy});
        while (!pq.empty()) {
            auto [d, x, y] = pq.top();
            pq.pop();
            d = -d;
            if (dist[x][y] < d) continue;
            for_nbd4(x, y, h, w, [d=d, x=x, y=y, &S, &dist, &pq](int u, int v) {
                    if (S[u][v] == '#') return;
                    if (dist[u][v] > dist[x][y] + 1) {
                        dist[u][v] = dist[x][y] + 1;
                        pq.push({-dist[u][v], u, v});
                    }
                });
        }

        if (dist[gx][gy] == INF) cout << "-1" << endl;
        else cout << d0 + dist[gx][gy] << endl;
    }
}