#include <iostream>
#include <vector>
#include <string>
#include <queue>
using namespace std;
using P = pair<int, int>;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int R, C; cin >> R >> C;
    int sy, sx; cin >> sy >> sx; sy--; sx--;
    int gy, gx; cin >> gy >> gx; gy--; gx--;
    vector<string> c(R);
    for (int i = 0; i < R; i++) cin >> c[i];
    vector<vector<int>> d(R, vector<int>(C, -1));
    vector<P> dxdy = {P(0, -1), P(-1, 0), P(1, 0), P(0, 1)};
    queue<P> que;
    d[sy][sx] = 0;
    que.push(P(sy, sx));
    while (!que.empty()) {
        P p = que.front(); que.pop();
        for (int i = 0; i < 4; i++) {
            int y = p.first + dxdy[i].first;
            int x = p.second + dxdy[i].second;
            if (y < 0 || x < 0 || y >= R || x >= C) continue;
            if (c[y][x] == '#' || d[y][x] >= 0) continue;
            d[y][x] = d[p.first][p.second] + 1;
            que.push(P(y, x));
        }
    }
    cout << d[gy][gx] << "\n";
}