#include <bits/stdc++.h>
using namespace std;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define REP(i, n) FOR(i,0,n)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define IREP(i, n) IFOR(i,0,n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(),v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x) distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL<<(n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v) { cout << #v << "=" << endl; REP(i_debug, v.size()){ cout << v[i_debug] << ","; } cout << endl; }
#define mdebug(m) { cout << #m << "=" << endl; REP(i_debug, m.size()){ REP(j_debug, m[i_debug].size()){ cout << m[i_debug][j_debug] << ","; } cout << endl;} }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for (auto &x : v) is >> x; return is; }
template<typename T> ostream &operator<<(ostream &os, vector<T> &v){ for(int i = 0; i < v.size(); i++) { cout << v[i]; if(i != v.size() - 1) cout << endl; }; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p){ cout << '(' << p.first << ',' << p.second << ')'; return os; }
template<typename T> void Out(T x) { cout << x << endl; }
template<typename T1, typename T2> void chOut(bool f, T1 y, T2 n) { if(f) Out(y); else Out(n); }

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;

int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};
//char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
//const int mod = 998244353;



signed main(){

    int H, W; cin >> H >> W;
    int ch, cw; cin >> ch >> cw; ch--; cw--;
    int dh, dw; cin >> dh >> dw; dh--; dw--;
    vector<string> S(H); cin >> S;

    mat dp(H, vec(W, INF));
    dp[ch][cw] = 0;
    v_Pii ls;
    queue<Pii> q1;
    q1.push(Pii(ch, cw));

    while(true){
        queue<Pii> q2;
        while(!q1.empty()){
            Pii p = q1.front();
            q2.push(p);
            q1.pop();

            int i = p.fi, j = p.se;
            REP(k, 4){
                int x = i + dx[k], y = j + dy[k];
                if(x < 0 || x >= H || y < 0 || y >= W || S[x][y] == '#') continue;
                if(dp[x][y] == INF){
                    dp[x][y] = dp[i][j];
                    q1.push(Pii(x, y));
                }
            }
        }

        while(!q2.empty()){
            Pii p = q2.front();
            q2.pop();
            int i = p.fi, j = p.se;
            FOR(u, -2, 3) FOR(v, -2, 3){
                int x = i + u, y = j + v;
                if(x < 0 || x >= H || y < 0 || y >= W || S[x][y] == '#') continue;
                if(dp[x][y] == INF){
                    dp[x][y] = dp[i][j] + 1;
                    q1.push(Pii(x, y));
                }
            }
        }
        if(q1.empty()) break;
    }
    

    chOut(dp[dh][dw] < INF, dp[dh][dw], -1);

    return 0;
}


Measured memory_bytes: 12564