/*~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
*$* WRITER:kakitamasziru/OxOmisosiru *$*
~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=*/
#ifdef LOCAL_JUDGE
#define _GLIBCXX_DEBUG
#endif
#include <iostream> // cout, endl, cin
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <iomanip>
#include <limits>//setprecision
//#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
//#include <unordered_set> //unordered_set
#include <stack> // stack
#include <deque> // deque
#include <math.h>//pow,,,
#include <cmath>//abs,,,
#include <bitset> // bitset
#define endl "\n";
using namespace std;

const long long INF = 4000000000000000001;
const int inf = 1001001001;
const int MOD = 1000000007;
typedef pair<long long,long long> P;

//Solve N^M. This, mod_pow use Iterative Square Method.
long long mod_pow(long long N, long long M) {
    if (M == 0) return 1;
    long long res = mod_pow((N * N) % MOD, M / 2);
    //最下位ビット(*N)が1の時は単独でNをかける
    if (M & 1) res = (res * N) % MOD;

    return res %= MOD;
}

long long gcd(long long a, long long b) {
    if (b == 0) return a;
    else return gcd(b, a % b);
}
long long lcm(long long a, long long b) {
    return a / gcd(a, b) * b ;
}



int main() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int H,W;cin >> H >> W;
    int wh,ww;cin >> wh >> ww;wh--;ww--;
    int gh,gw;cin >> gh >> gw;gh--;gw--;
    vector<vector<char>> ban(H,vector<char>(W));
    for(int i = 0;i<H;i++){
        for(int j = 0;j<W;j++){
            cin >> ban.at(i).at(j);
        }
    }
    deque<pair<int,pair<int,int>>> Q;
    Q.push_front(make_pair(0,make_pair(wh,ww)));
    vector<vector<bool>> seen(H,vector<bool>(W));
    int ans = inf;
    vector<vector<int>> mini(H,vector<int>(W));
    for(int i = 0;i<H;i++) for(int j = 0;j<W;j++) mini.at(i).at(j) = inf;
    while(!Q.empty()){
        pair<int,pair<int,int>> p = Q.front();Q.pop_front();
        int nh = p.second.first,nw = p.second.second,cost = p.first;
        if(nh == gh && nw == gw){
            ans = min(ans,cost);
        }
        mini.at(nh).at(nw) = min(mini.at(nh).at(nw),cost);
        cost = min(cost,mini.at(nh).at(nw));
        seen.at(nh).at(nw) = true;
        for(int i = -1;i<=1;i++){
            for(int j = -1;j<=1;j++){
                if(i == j || i == -1 && j == 1 || i == 1 && j == -1) continue;
                if(nh+i < 0 || nh+i >= H || nw+j < 0 || nw+j >= W) continue;
                if(ban.at(nh+i).at(nw+j) == '#') continue;
                if(seen.at(nh+i).at(nw+j)) continue;
                Q.push_front(make_pair(cost,make_pair(nh+i,nw+j)));
                seen.at(nh+i).at(nw+j) = true;
            }
        }
        for(int i = -2;i<=2;i++){
            for(int j = -2;j<=2;j++){
                if(nh+i < 0 || nh+i >= H || nw+j < 0 || nw+j >= W) continue;
                if(ban.at(nh+i).at(nw+j) == '#') continue;
                if(seen.at(nh+i).at(nw+j)) continue;
                Q.push_back(make_pair(cost+1,make_pair(nh+i,nw+j)));
                //seen.at(nh+i).at(nw+j) = true;
            }
        }
    }
    if(ans == inf){
        cout << -1 << endl;
    }
    else{
        cout << ans << endl;
    }
}


Measured memory_bytes: 10116