#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define REP(a,b) for(int a=0;a<(b);++a)
#define REP1(i,n) for(int i=1;i<=(n);++i)
#define debug(x) cerr<<#x<<": "<<x<<'\n'
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define YES() printf("YES\n")
#define NO() printf("NO\n")
#define isYES(x) printf("%s\n",(x) ? "YES" : "NO")
#define Yes() printf("Yes\n")
#define No() printf("No\n")
#define isYes(x) printf("%s\n",(x) ? "Yes" : "No")
#define isPossible(x) printf("%s\n",(x) ? "Possible" : "Impossible")
#define SZ(x) ((int)(x).size())
#define pb push_back
#define mp make_pair
// #define INF (1<<29)

const long long INF = 1LL<<50;

#define Sp(p) cout<<setprecision(25)<< fixed<<p<<endl
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
#define pie 3.14159265358979323846
using namespace std;
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
typedef pair<int, P> PP;
typedef pair<ll, LP> LPP;
template<class T=int>
T in(){T x;cin>>x;return (x);}
template<class T>
void print(T& x){cout<<x<<'\n';}

const int MOD =(int)1e9+7;
// const int mod =(int)998244353;
const int mod =(int)1e9+7;

const int MAX =510000;
ll fac[MAX],finv[MAX],inv[MAX];
void COMint(){
    fac[0]=fac[1]=1;
    finv[0]=finv[1]=1;
    inv[1]=1;
    for(int i=2;i<MAX;i++){
        fac[i]=fac[i-1]*i%MOD;
        inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;
        finv[i]=finv[i-1]*inv[i]%MOD;
    }
}
ll COM(int n,int k){
    if(n<k) return 0;
    if(n<0||k<0)return 0;
    return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD;
}
ll gcd(ll a,ll b){
    if(a<0)a=-a;
    if(b<0)b=-b;
    if(b==0)return a;
    if(a>b){
        swap(a,b);
    }
    return gcd(a,b%a);
}
ll lcm(ll a,ll b){
  if(a<0)a=-a;
  if(b<0)b=-b;
    ll g;g=gcd(a,b);
    return b/g*a;
}
bool compare_by_b(pair<int, int> a, pair<int, int> b) {
    if(a.second != b.second){
        return a.second < b.second;
    }else{
        return a.first < b.first;
    }
}
bool compare_by_a(pair<int, int> a, pair<int, int> b) {
    if(a.first != b.first){
        return a.first < b.first;
    }else{
        return a.second < b.second;
    }
}
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;
}
//int N, M, K, T, H, W, L, R;
long long int N, M, K, T, H, W, L, R;
int main() {
    ios::sync_with_stdio(false);
    cin>>H>>W;
    int sx,sy,gx,gy;
    cin>>sy>>sx>>gy>>gx;
    sy--;sx--;gy--;gx--;
    vector<string>s(H);
    REP(i,H)cin>>s[i];
    vector<vi>dis(H,vi(W,MOD));
    deque<pair<int,int>>Q;
    Q.push_back({sy,sx});
    dis[sy][sx]=0;
    int dir[]={1,0,-1,0,1};
    while(!Q.empty()){
        int cx,cy;
        tie(cy,cx)=Q.front();
        Q.pop_front();
        for(int i=0;i<4;i++){
            int ny=cy+dir[i];
            int nx=cx+dir[i+1];
            if(ny<0||nx<0||ny>=H||nx>=W)continue;
            if(s[ny][nx]=='#')continue;
            if(dis[ny][nx]>dis[cy][cx]){
                dis[ny][nx]=dis[cy][cx];
                Q.push_front({ny,nx});
            }
        }
        for(int i=-2;i<=2;i++){
            for(int j=-2;j<=2;j++){
                int ny=cy+i;
                int nx=cx+j;
                if(ny<0||nx<0||ny>=H||nx>=W)continue;
                if(s[ny][nx]=='#')continue;
                if(dis[ny][nx]>dis[cy][cx]+1){
                    dis[ny][nx]=dis[cy][cx]+1;
                    Q.push_back({ny,nx});
                }
            }
        }
    }
    if(dis[gy][gx]>=MOD)dis[gy][gx]=-1;
    cout<<dis[gy][gx]<<endl;
    return 0;
} 
 

Measured memory_bytes: 8692