#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < n; ++i)
typedef long long ll;
using namespace std;
const int INF = 1e9;

int main() {
    int h, w;
    cin >> h >> w;
    int sy, sx, gy, gx;
    cin >> sy >> sx >> gy >> gx;
    sy--, sx--, gy--, gx--;
    vector<string> s(h);
    rep(i, h) cin >> s[i];

    vector<vector<int>> d(h, vector<int>(w, INF));
    queue<pair<int, int>> que;
    que.push({sy, sx});
    d[sy][sx] = 0;

    int dx[] = {1, -1, 0, 0};
    int dy[] = {0, 0, 1, -1};
    while (!que.empty()) {
        auto now = que.front();
        que.pop();
        rep(i, 4) {
            int ny = now.first + dy[i];
            int nx = now.second + dx[i];

            if (ny >= 0 && nx >= 0 && ny < h && nx < w && s[ny][nx] == '.' && d[ny][nx] == INF) {
                d[ny][nx] = d[now.first][now.second] + 1;
                que.push({ny, nx});
            }
        }
    }

    cout << d[gy][gx] << endl;

    return 0;
}