//#include <tourist>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF = 1e9;
const ll LINF = ll(1e18);
const int MOD = 1000000007;
const int dx[4] = {0, 1, 0, -1}, dy[4] = {-1, 0, 1, 0};
const int Dx[8] = {0, 1, 1, 1, 0, -1, -1, -1}, Dy[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
#define yes cout << "Yes" << endl
#define YES cout << "YES" << endl
#define no cout << "No" << endl
#define NO cout << "NO" << endl
#define rep(i, n) for (int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()
#define debug(v)          \
    cout << #v << ":";    \
    for (auto x : v)      \
    {                     \
        cout << x << ' '; \
    }                     \
    cout << endl;
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;
}
//cout<<fixed<<setprecision(15);有効数字15桁
//-std=c++14
//-std=gnu++17
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
// ダイクストラ
//LINFにしてあるよ
struct edge
{
    ll to, cost;
};
typedef pair<ll, ll> P;
struct graph
{
    ll V;
    vector<vector<edge>> G;
    vector<ll> d;
    //vector<ll> count;経路の本数
    //vector<ll> prev; // prev[v] := v から復元できる辺たち
    graph(ll n)
    {
        init(n);
    }

    void init(ll n)
    {
        V = n;
        G.resize(V);
        d.resize(V);
        //count.resize(V);
        rep(i, V)
        {
            d[i] = LINF;
            //count[i] = 0;
        }
    }

    void add_edge(ll s, ll t, ll cost)
    {
        edge e;
        e.to = t, e.cost = cost;
        G[s].push_back(e);
    }

    void dijkstra(ll s)
    {
        rep(i, V)
        {
            d[i] = LINF;
            //count[i] = 0;
        }
        d[s] = 0;
        //count[s] = 1;
        priority_queue<P, vector<P>, greater<P>> que;
        que.push(P(0, s));
        while (!que.empty())
        {
            P p = que.top();
            que.pop();
            ll v = p.second;
            if (d[v] < p.first)
                continue;
            for (auto e : G[v])
            {
                if (d[e.to] > d[v] + e.cost)
                {
                    d[e.to] = d[v] + e.cost;
                    que.push(P(d[e.to], e.to));
                    //count[e.to] = count[v];
                    // 復元のための
                    //prev[e.to]=v;
                }
                /*
        else if (d[e.to] == d[v] + e.cost)
                {
                    count[e.to] += count[v];
                    count[e.to] %= MOD;
                }
                */
            }
        }
    }
};
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int h, w;
    cin >> h >> w;
    int ch, cw;
    cin >> ch >> cw;
    int dh, dw;
    cin >> dh >> dw;
    ch--;
    dh--;
    cw--;
    dw--;
    vector<string> s(h);
    rep(i, h) cin >> s[i];
    graph g(h * w);
    rep(i, h)
    {
        rep(j, w)
        {
            if (s[i][j] == '#')
                continue;
            rep(k, 4)
            {
                int d = dx[k];
                int e = dy[k];
                if (i + d >= h || j + e >= w || i + d < 0 || j + e < 0)
                    continue;
                if (s[i + d][j + e] == '#')
                    continue;
                g.add_edge(i * w + j, (i + d) * w + j + e, 0);
            }
            for (int k = -2; k <= 2; k++)
            {
                for (int l = -2; l <= 2; l++)
                {
                    int d = k;
                    int e = l;
                    if (i + d >= h || j + e >= w || i + d < 0 || j + e < 0)
                        continue;
                    if (s[i + d][j + e] == '#')
                        continue;
                    g.add_edge(i * w + j, (i + d) * w + j + e, 1);
                }
            }
        }
    }
    g.dijkstra(ch*w+cw);
    if (g.d[dh * w + dw]!=LINF)
        cout << g.d[dh * w + dw] << "\n";
    else cout<<-1<<"\n";
}


Measured memory_bytes: 206040