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

#define int long long
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define range(i,a,b) ((a)<=(i) && (i)<(b))
#define debug(x) cout << #x << " = " << (x) << endl;
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
#define SP << " " <<

typedef long long ll;
typedef pair<int, int> P;
typedef tuple<int, int, int> T;
typedef vector<int> vec;
typedef vector<P> pvec;
typedef vector<vector<int>> vvec;
typedef vector<vector<P>> pvvec;
typedef priority_queue<int> PQI;
typedef priority_queue<P> PQP;
typedef priority_queue<int,vector<int>,greater<int>> PQIG;
typedef priority_queue<P,vector<P>,greater<P>> PQPG;

const vector<int> DX = {0, -1, 0, 1, 1, 1, -1, -1};
const vector<int> DY = {1, 0, -1, 0, 1, -1, 1, -1};
constexpr int MOD = (1000000007);
// const int MOD = (998244353);
// const int INF = (1 << 30); // 1073741824
const ll INF = (1LL << 60); // 1152921504606846976
const double PI = (3.141592653589794);
const double EPS = (0.0000000001); // 10^(-10)

template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return 1;} return 0;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return 1;} return 0;}
template<class T> inline T ceil(T a, T b) {return T((a + b - 1) / b);}
template<class T> inline T round(T a, T b) {return T(a / b);}
template< typename T1, typename T2 > istream &operator>>(istream &is, pair< T1, T2 > &p) { is >> p.first >> p.second; return is; }
template <class T> inline void out(T &a) { bool flag=true; for(auto&x:a){if(flag) {flag=false;} else{ cout << ' '; } cout<<x; } cout << endl; }



//----------------------------------------------------------------
int nmax=200000; // 2*(10^5)
vvec G(nmax);





void solve4ts()
{
    
    
    int h,w;
    cin>>h>>w;
    int ch,cw,dh,dw;
    cin>>ch>>cw>>dh>>dw;
    ch--,cw--,dh--,dw--;
    char s[h][w];
    int c[h][w];
    rep(i,h) rep(j,w){
        cin>>s[i][j];
        c[i][j]=-1;
    }

    queue<P> q;
    queue<P> vq;
    q.push(P(ch,cw));
    int now=0;
    while(true){
        while(!q.empty()){
            int nh,nw;
            tie(nh,nw)=q.front();
            vq.push(q.front());
            q.pop();
            rep(i,4){
                int nx=nh+DX[i];
                int ny=nw+DY[i];
                if(range(nx,0,h)&&range(ny,0,w)&&s[nx][ny]=='.'&&c[nx][ny]==-1){
                    c[nx][ny]=now;
                    q.push(P(nx,ny));
                }
            }
        }
        now++;
        if(vq.empty()){
            break;
        }
        while(!vq.empty()){
            int nh,nw;
            tie(nh,nw)=vq.front();
            vq.pop();
            for(int i=-2;i<=2;i++){
                for(int j=-2;j<=2;j++){
                    int nx=nh+i;
                    int ny=nw+j;
                    if(range(nx,0,h)&&range(ny,0,w)&&s[nx][ny]=='.'&&c[nx][ny]==-1){
                        c[nx][ny]=now;
                        q.push(P(nx,ny));
                    }
                }
            }
        }
    }
    // rep(i,h) {
    //     rep(j,w){
    //     cout<<c[i][j];
    //     }
    //     cout<<endl;
    // }
    cout<<c[dh][dw]<<endl;
}
//-----------------------------------------------------------------

signed main(){ ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(15);
    int repeat = 1;
    // cin >> repeat;
    while(repeat--) solve4ts();
}

/*

g++ -std=c++1z code.cpp
./a.out

*/

Measured memory_bytes: 16928