#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i, n) for (int i = 0; i < (int) (n); i++)
#define reps(i, n) for (int i = 1; i <= (int) (n); i++)
#define all(x) (x).begin(), (x).end()
#define uniq(x) (x).erase(unique(all(x)), (x).end())
#define bit(n) (1LL << (n))
#define cdiv(a, b) (((a) - 1) / (b) + 1)
#define dump(x) cerr << #x " = " << (x) << endl
using vint = vector<int>;
using vvint = vector<vint>;
using pint = pair<int, int>;
using vpint = vector<pint>;
template<typename T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
constexpr double PI = 3.1415926535897932384626433832795028;
constexpr int DY[9] = {0, 1, 0, -1, 1, 1, -1, -1, 0};
constexpr int DX[9] = {1, 0, -1, 0, 1, -1, -1, 1, 0};
int gcd(int a, int b) {
    while (b) { swap(a %= b, b); }
    return a;
}
int lcm(int a, int b) { return a / gcd(a, b) * b; }
int sign(int x) { return (x > 0) - (x < 0); }
template<typename T> void fin(T mes) {
    cout << mes << endl;
    exit(0);
}
template<typename T, typename U> bool chmax(T &a, const U &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> bool chmin(T &a, const U &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &rhs) {
    os << "(" << rhs.first << ", " << rhs.second << ")";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const vector<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const deque<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const set<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const map<T, U> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
struct setup {
    static constexpr int PREC = 20;
    setup() {
        cout << fixed << setprecision(PREC);
        cerr << fixed << setprecision(PREC);
    };
} setup;

template<typename M>
std::vector<typename M::T> dijkstra(const std::vector<std::vector<int>> &adj,
                                    const std::vector<std::vector<typename M::E>> &cost,
                                    int s) {
    using T = typename M::T;
    int n = adj.size();
    assert(0 <= s && s < n);
    std::vector<T> ret(n, M::ab());
    using P = std::pair<T, int>;
    auto c = [&](P a, P b) -> bool { return M::gr(a.first, b.first); };
    std::priority_queue<P, std::vector<P>, decltype(c)> pq(c);
    ret[s] = M::id();
    pq.push({ret[s], s});
    while (!pq.empty()) {
        P p = pq.top();
        pq.pop();
        int v = p.second;
        if (M::gr(p.first, ret[v])) { continue; }
        for (int i = 0; i < adj[v].size(); i++) {
            int u = adj[v][i];
            T dist = M::op(ret[v], cost[v][i]);
            if (M::gr(ret[u], dist)) { ret[u] = dist, pq.push({ret[u], u}); }
        }
    }
    return ret;
}

struct int_dij {
    using T = int;
    using E = int;
    static T id() { return 0; }
    static T ab() { return std::numeric_limits<T>::max(); }
    static T op(const T &a, const E &b) { return a == ab() ? ab() : a + b; }
    static bool gr(const T &a, const T &b) { return a > b; }
};

signed main() {
  int H,W,Ch,Cw,Dh,Dw;
  cin>>H>>W>>Ch>>Cw>>Dh>>Dw;
  Ch--,Cw--,Dh--,Dw--;
  vector<string> S(H);
  rep(i,H)cin>>S[i];
  vvint adj(H*W,vint()),cost(H*W,vint());
  rep(i,H){
    rep(j,W){
      for(int dx=-2;dx<=2;dx++){
        for(int dy=-2;dy<=2;dy++){
          int ny=i+dy,nx=j+dx;
          if((ny==i&&nx==j)||ny<0||nx<0||ny>=H||nx>=W||S[ny][nx]=='#')continue;
          if(abs(ny-i)+abs(nx-j)==1){
            adj[i*W+j].emplace_back(ny*W+nx);
            cost[i*W+j].emplace_back(0);
          }else{
            adj[i*W+j].emplace_back(ny*W+nx);
            cost[i*W+j].emplace_back(1);
          }
        }
      }
    }
  }
  int ans=dijkstra<int_dij>(adj,cost,Ch*W+Cw)[Dh*W+Dw];
  if(ans==LLONG_MAX)ans=-1;
  cout<<ans<<endl;
}

Measured memory_bytes: 338980