#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
#define get_unique(x) x.erase(unique(all(x)), x.end());
typedef long long ll;
typedef complex<double> Complex;
const int INF = 1e9;
const ll MOD = 1e9 + 7;
const ll LINF = 1e18;
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}

vector<int> dy = {0, 1, 0, -1};
vector<int> dx = {1, 0, -1, 0};
int main() {
    int h, w, sy, sx, gy, gx;
    cin >> h >> w >> sy >> sx >> gy >> gx;
    sy--;
    sx--;
    gy--;
    gx--;
    auto v = make_vec<char>(h, w);
    rep(i, h) rep(j, w) cin >> v[i][j];

    auto d = make_vec<int>(h, w);
    rep(i, h) rep(j, w) d[i][j] = -1;
    queue<pair<int, int>> q;
    d[sy][sx] = 0;
    q.push({sy, sx});
    while (sz(q)) {
        int y, x;
        tie(y, x) = q.front();
        q.pop();
        rep(k, 4) {
            int ny = y + dy[k], nx = x + dx[k];
            if (!(0 <= ny && ny < h && 0 <= nx && nx < w)) continue;
            if (v[ny][nx] != '.') continue;
            if (d[ny][nx] != -1) continue;
            d[ny][nx] = d[y][x] + 1;
            q.push({ny, nx});
        }
    }

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