#include <bits/stdc++.h>
using namespace std;
#define REP(i,x,n) for(int i=x;i<(int)n;i++)
#define rep(i,n) REP(i,0,n)
#define sp(p) cout<<setprecision(16)<<fixed<<p<<endl;
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define SORT(a) sort(all(a))
#define RSORT(a) sort(rall(a))
#define UNIQ(a) unique(all(a))
#define UNIQNUM(a) UNIQ(a)-a.begin()
#define UNIQIT(a) a.erase(UNIQ(a), a.end());
#define VOUT(v,i) rep(i,v.size())cout<<v[i]<<(i==v.size()-1?"\n":" ");
#define vout(v) VOUT(v,z);
#define vdbg(v,i) cout<<#v<<": ";for(int i=0;i<(int)v.size();i++){cout<<v[i]<<" ";}cout<<"\n";
#define vmin(v) *min_element(all(v))
#define vmax(v) *max_element(all(v))
#define vsum(v) accumulate(all(v), 0LL)
#define MOUT(m,r,c) rep(i,r){rep(j,c){cout<<m[i][j]<<" ";}cout<<endl;}
#define mout(m) MOUT(m,m.size(),m[0].size())
#define debg(a) cout<<#a<<": "<<a<<endl;
#define show(a) for(cont &y:a){for(cont &x:y){cout<<x<<" ";}cout<<endl;}
#define digit(a) to_string(a).length();
template<class T>inline int out(const T &t){ print(t); putchar('\n'); return 0; }
// template<class T>inline T gcd(T a,T b){if(b==0)return a; return(gcd(b,a%b));}
// template<class T>inline T lcm(T a,T b){return a/gcd(a,b)*b;}
bool is_palindrome(string s){return s == string(s.rbegin(),s.rend());}
#define popcount __builtin_popcount
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> P;
typedef vector<ll> V;
typedef vector<vector<ll>> VV;
// const long long MOD=1000000007;
const long long INF = 1e18;
#define EPS (1e-7)
#define PI (acos(-1))
template<class T>
inline bool chmax(T &a, T b) {
    if(a < b) { a = b; return true; }
    return false;
}
template<class T>
inline bool chmin(T &a, T b) {
    if(a > b) { a = b; return true; }
    return false;
}

const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};

const int wx[20] = {1,-1,-1, 1, 2, 2, 2, 2, 2, 1, 1, 0, 0,-1,-1,-2,-2,-2,-2,-2};
const int wy[20] = {1, 1,-1,-1, 2, 1, 0,-1,-2, 2,-2, 2,-2, 2,-2, 2, 1, 0,-1,-2};

ll h, w;
bool isRange(ll y, ll x){return(0<=y&&y<h&&0<=x&&x<w);}

int main(){
    // ll h, w;
    cin >> h >> w;
    ll ch, cw, dh, dw;
    cin >> ch >> cw >> dh >> dw;
    vector<vector<char>> s(h, vector<char>(w));
    for (ll i = 0; i < h; i++) {
        for (ll j = 0; j < w; j++) {
            cin>>s[i][j];
        }
    }

    // mout(s);
    vector<vector<ll>> n(h, vector<ll>(w, -1));

    queue<P> q;
    queue<P> wq;
    P p;
    ch--,cw--;
    dh--,dw--;
    q.push(P(ch,cw));
    wq.push(P(ch,cw));
    n[ch][cw]=0;

    while(q.size()){
        while(q.size()){
            p=q.front();
            q.pop();
            wq.push(P(p.first,p.second));
            // for (long long i = 0; i < 20; i++) {
            //     ll ny=p.first+wy[i], nx=p.second+wx[i];
            //     if(isRange(ny,nx) && s[ny][nx]=='.' && n[ny][nx]==-1){
            //         n[ny][nx]=n[p.first][p.second]+1;
            //         q.push(P(ny,nx));
            //     }
            // }
            for (long long i = 0; i < 4; i++) {
                ll ny=p.first+dy[i], nx=p.second+dx[i];
                if(isRange(ny,nx) && s[ny][nx]=='.' && (n[ny][nx]>n[p.first][p.second] || n[ny][nx]==-1)){
                    n[ny][nx]=n[p.first][p.second];
                    // if(n[ny][nx]!=-1){
                    //     chmin(n[ny][nx],n[p.first][p.second]);
                    //     chmin(n[p.first][p.second],n[ny][nx]);
                    // }
                    q.push(P(ny,nx));
                    wq.push(P(ny,nx));
                }
            }
            // if(ch==0&&cw==0) {
            //     mout(n);
            //     cout << endl;
            // }
        }
        // mout(n); cout << endl;

        while(wq.size()){
            p=wq.front();
            wq.pop();
            for (long long i = 0; i < 20; i++) {
                ll ny=p.first+wy[i], nx=p.second+wx[i];
                if(isRange(ny,nx) && s[ny][nx]=='.' && n[ny][nx]==-1){
                    n[ny][nx]=n[p.first][p.second]+1;
                    q.push(P(ny,nx));
                    // wq.push(P(ny,nx));
                }
            }
        }
        // mout(n); cout << endl;
    }
    // mout(n);

    cout << n[dh][dw] << endl;

    return 0;
}


Measured memory_bytes: 12736