#include <iostream>
#include <algorithm>
#include <utility>
#include <string>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <math.h>
#include <string.h>
#include <iomanip>
#include <numeric>
#include <cstdlib>
#include <cstdint>
#include <cmath>
#include <functional>
#include <limits>
#include <cassert>
#include <bitset>
 
using namespace std;
 
/* template */
 
using ll = long long;
 
void debug_out() { std::cout << std::endl; }
 
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}
 
#ifdef LOCAL
#define debug(...) cout << "debug: "; debug_out(__VA_ARGS__)
#else
#define debug(...) 
#endif
 
#define rep(i, a, n) for (int i = (int)(a); i < (int)(n); i++)
#define rrep(i, a, n) for (int i = ((int)(n-1)); i >= (int)(a); i--)
#define Rep(i, a, n) for (long long i = (long long)(a); i< (long long)(n); i++)
#define RRep(i, a, n) for (long long i = ((long long)(n-1ll)); i>=(long long)(a); i--)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
 
template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}
 
struct Edge{
    int to;
    ll weight;
    Edge(int t, ll w) : to(t), weight(w){ }
};
 
struct edge{
    int from;
    int to;
    ll weight;
    edge(int f,int t,ll w) : from(f), to(t), weight(w){ }
};
 
 
using Graph = vector<vector<Edge>>;
using graph = vector<vector<int>>;
using edges = vector<edge>;
 
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;
}
 
template <class T>
T lcm(T a, T b){
    return (a*b)/gcd(a,b);
}
 
ll ctoi(char c) {
	switch (c) {
	case '0': return 0; case '1': return 1; case '2': return 2;
	case '3': return 3; case '4': return 4; case '5': return 5;
	case '6': return 6; case '7': return 7; case '8': return 8;
	case '9': return 9;  default: return 0;
	}
}
 
constexpr ll LNF = 1LL<<50;
 
constexpr int INF = 1e9+7;
 
const long double PI=3.14159265358979323846;
 
 
vector<int> dx = {1,0,-1,0};
vector<int> dy = {0,1,0,-1};
 
/* template */

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int h,w; cin >> h >> w;
    pair<int,int> p,q;
    cin >> p.first >> p.second;
    cin >> q.first >> q.second;
    p.first--; p.second--;
    q.first--; q.second--;
    vector<string> s(h);
    rep(i,0,h){
        cin >> s[i];
    }
    vector<vector<int>> seen(h,vector<int>(w,INF)),m(h,vector<int>(w,0));
    seen[p.first][p.second] = 0;
    queue<pair<int,int>> que;
    int index = 0;
    que.push(p);
    while(!que.empty()){
        vector<pair<int,int>> r;
        while(!que.empty()){
            auto d = que.front(); que.pop();
            int x = d.first, y = d.second;
            int flag = 0;
            rep(i,0,4){
                int nx = x + dx[i], ny = y + dy[i];
                if(0<= nx && nx < h && 0<= ny && ny <w && index < seen[nx][ny] && s[nx][ny]!='#'){
                    que.push(make_pair(nx,ny));
                    seen[nx][ny] = index;
                    continue;
                }
                flag++;
            }
            if(flag==0) continue;
            rep(i,0,5){
                rep(j,0,5){
                    int nx = x + i - 2;
                    int ny = y + j - 2;
                    if(0<= nx && nx < h && 0<= ny && ny <w && index+1 < seen[nx][ny] && s[nx][ny]!='#' && m[nx][ny]==0){
                        r.emplace_back(make_pair(nx,ny));
                        seen[nx][ny] = index+1;
                        m[nx][ny] = index+1;
                    }
                }
            }
        }
        if(seen[q.first][q.second]<INF){
            break;
        }
        for(auto &x : r){
            if(m[x.first][x.second]==seen[x.first][x.second]){
                que.push(x);
            }
        }
        index++;
    }
    if(seen[q.first][q.second]<INF){
        cout << seen[q.first][q.second] << endl;
    }
    else{
        cout << -1 << endl;
    }
}


Measured memory_bytes: 12700