#pragma region header
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define rev(i, n) for(int i = (int)(n - 1); i >= 0; i--)
#define rev1(i, n) for(int i = (int)(n); i > 0; i--)
#define pb push_back
#define all(v) (v).begin(), (v).end()
#define resort(v) sort((v).rbegin(), (v).rend())
#define vi vector<int>
#define vvi vector<vector<int>>
#define vc vector<char>
#define vvc vector<vector<char>>
#define vb vector<bool>
#define vvb vector<vector<bool>>
using ll = long long;
using P = pair<int, int>;
/* ----------------よく使う数字や配列----------------- */
int dx[] = {1,0,-1,0};
int dy[] = {0,1,0,-1};
constexpr ll mod = 1e9+7;
constexpr ll inf = INT32_MAX/2;
constexpr ll INF = LLONG_MAX/2;
constexpr long double eps = DBL_EPSILON;
constexpr long double pi = 3.141592653589793238462643383279;
/* ----------------------end----------------------- */

/* --------------------テンプレート------------------ */
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
/* ----------------------end----------------------- */

/* --------------------ライブラリ-------------------- */
ll fact(int i) {       //階乗
    if (i == 0) return 1;
    return (fact(i - 1)) * i % mod;
}
ll gcd(ll a, ll b) {        //最大公約数
    if(b == 0) return a;
    return gcd(b, a % b); 
}
ll lcm(ll a, ll b) {      //最小公倍数
    return a * b / gcd(a, b);
}
int keta(ll n) {        //桁数を求める
    if(n == 0) return 1;
    int count = 0;
    while(n != 0) {
        n /= 10;
        count++;
    }
    return count;
}
ll ketasum(ll n) {    //各桁の和
    ll sum = 0;
    while(n != 0) {
        sum += n % 10;
        n /= 10;
    }
    return sum;
}
/* ----------------------end----------------------- */
#pragma endregion
signed main() {
    int h,w;cin >> h >> w;
    int sx,sy,gx,gy;cin >> sx >> sy >> gx >> gy;sx--;sy--;gx--;gy--;
    vvb bo(h,vb(w,false));
    vvc mp(h,vc(w));
    vvi ans(h,vi(w,inf));
    rep(i, h) {
        rep(j, w) {
            // char c;cin >> c;
            // if(c=='#') bo[i][j]=true;
            cin >> mp[i][j];
        }
    }
    ans[sx][sy]=0;
    deque<P> deq;
    deq.push_front({sx,sy});
    while(!deq.empty()) {
        P p = deq.front();
        deq.pop_front();
        rep(i, 4) {
            int x = p.first+dx[i],y=p.second+dy[i];
            if(x<0||x>=h||y<0||y>=w)continue;
            if(mp[x][y]=='.'&&ans[x][y]>ans[p.first][p.second]){
                deq.push_front({x,y});
                // cout << "(x,y)=(" << x << "," << y << ")" << endl;
                ans[x][y]=ans[p.first][p.second];
                // bo[x][y]=true;
                // cout << "OK" << endl;
            }
            else if(mp[x][y]=='#'&&!bo[x][y]/*&&ans[x][y]>ans[p.first][p.second]+1*/) {
                // cout << "OK\n";
                for(int s = -2;s<=2;s++) {
                    for(int t = -2;t<=2;t++) {
                        if(i==0&&s==2)continue;
                        if(i==1&&t==2)continue;
                        if(i==2&&s==-2)continue;
                        if(i==3&&t==-2)continue;
                        int X = x+s,Y=y+t;
                        if(X<0||X>=h||Y<0||Y>=w||mp[X][Y]=='#') continue;
                        deq.push_back({X,Y});
                        ans[X][Y]=min(ans[p.first][p.second]+1,ans[X][Y]);
                        bo[x][y]=true;
                        // cout << "{X,Y}={" << X << "," << Y << "}\n";
                    }
                }
            }
        }
    }
    if(ans[gx][gy]==inf)puts("-1");
    else cout << ans[gx][gy] << endl;
    /*rep(i, h) {
        rep(j, w) {
            cout << ans[i][j];
            if(j==w-1)cout << endl;
            else cout << ' ';
        }
    }*/
    return 0;
}

Measured memory_bytes: 13892