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

#define REP(i,n) for(ll i=0;i<(ll)n;i++)
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define spa << " " <<
#define fi first
#define se second
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()

using ld = long double;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<long, long>;
using pdd = pair<ld, ld>;

template<typename T> struct V : vector<T> { using vector<T>::vector; };
V() -> V<ll>;
V(size_t) -> V<ll>;
template<typename T> V(size_t, T) -> V<T>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class S, class T> ostream& operator << (ostream& os, const pair<S, T> v){os << "(" << v.first << ", " << v.second << ")"; return os;}
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> ostream& operator<<(ostream& os, const vector<vector<T>> &v){ for(auto &e : v){os << e << "\n";} return os;}
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;

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 (a>b) { a=b; return 1; } return 0; }
void fail() { cout << -1 << '\n'; exit(0); }
inline int popcount(const int x) { return __builtin_popcount(x); }
inline int popcount(const ll x) { return __builtin_popcountll(x); }
template<typename T> void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cerr<<v[i][0];for(ll j=1;j<w;j++)cerr spa v[i][j];cerr<<endl;}};
template<typename T> void debug(vector<T>&v,ll n){if(n!=0)cerr<<v[0];
for(ll i=1;i<n;i++)cerr spa v[i];
cerr<<endl;};

// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const ll mod = (int)1e9 + 7;
//const ll mod = 998244353;
const int INF = (1ll<<30);

vector<vector<int>> grid_bfs(const vector<string> &S, ll sx, ll sy, const char wall){
    // start 文字が入っているところから始まる多始点BFS
    // wall があるセルには入れない．この辺は適当に変更

    const int num_dir = 4;
    const int dx[] = {0, -1, 0, 1};
    const int dy[] = {1, 0, -1, 0}; 

    const int H = S.size();
    const int W = S[0].size();
    vector<vector<int>> dist(H, vector<int>(W, INF));
    deque<pair<int, int>> qu;

    // initialization
    // for(int i=0;i<H;i++){
    //     for(int j=0;j<W;j++){
    //         if(S[i][j] == start){
    //             qu.emplace(i, j);
    //             dist[i][j] = 0;
    //         }
    //     }
    // }

    qu.emplace_back(sx, sy);
    dist[sx][sy] = 0;

    // BFS
    while(!qu.empty()){
        auto p = qu.front();qu.pop_front();

        for(int idx=0;idx<num_dir;idx++){
            int ni = p.first + dx[idx];
            int nj = p.second + dy[idx];

            if(ni<0 or nj<0 or ni>H-1 or nj>W-1) continue;
            if(dist[ni][nj] <= dist[p.first][p.second]) continue;
            if(S[ni][nj] == wall) continue;
            
            dist[ni][nj] = dist[p.first][p.second];
            qu.emplace_front(ni, nj);
        }

        for(ll hx = -2;hx<=2;hx++){
            for(ll hy = -2;hy<=2;hy++){
                int ni = p.first + hx;
                int nj = p.second + hy;

                if(ni<0 or nj<0 or ni>H-1 or nj>W-1) continue;
                if(dist[ni][nj] <= dist[p.first][p.second]+1) continue;
                if(S[ni][nj] == wall) continue;
                
                dist[ni][nj] = dist[p.first][p.second] + 1;
                qu.emplace_back(ni, nj);
            }
        }
    }

    //debug(dist, H, W);
    return dist;
}

int main(){

    ll H, W, sx, sy, tx, ty;
    cin >> H >> W >> sx >> sy >> tx >> ty;
    sx--, sy--, tx--, ty--;

    V<string> S(H);
    REP(i, H) cin >> S[i];

    auto dist = grid_bfs(S, sx, sy, '#');

    //dump(dist)

    cout << (dist[tx][ty] == INF ? -1 : dist[tx][ty]) << endl;

    return 0;
}

Measured memory_bytes: 8772