#include"bits/stdc++.h"

using namespace std; 

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef vector<LL> VL;
typedef vector<VL> VVL;
typedef pair<LL, LL> PLL;
typedef vector<PLL> VPLL;
typedef priority_queue<LL> PQ_DESC;
typedef priority_queue<LL, VL, greater<LL>> PQ_ASC;
typedef priority_queue<PII> PQ_DESC_PII;
typedef priority_queue<PII, vector<PII>, greater<PII>> PQ_ASC_PII;
typedef priority_queue<VL> PQ_DESC_VL;
typedef priority_queue<VL, vector<VL>, greater<VL>> PQ_ASC_VL;
typedef priority_queue<PLL> PQ_DESC_PLL;
typedef priority_queue<PLL, vector<PLL>, greater<PLL>> PQ_ASC_PLL;

#define ALL(c) (c).begin(),(c).end()
#define PB push_back
#define MP make_pair
#define SORT_ASC(c) sort(ALL(c))
//#define SORT_DESC(c) sort(ALL(c), greater<typeof(*((c).begin()))>())
#define SORT_DESC(c) sort((c).rbegin(),(c).rend())
#define REV(c) reverse((c).begin(), (c).end())
#define SIZE(a) int((a).size())

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define ROF(i,a,b) for(int i=(b-1);i>=(a);--i)
#define REP(i,n) FOR(i,0,n)
#define PER(i,n) ROF(i,0,n)

const double EPS = 1e-10;
const double PI  = acos(-1.0);
const int LARGE_INT = 1e9+100;
const int INF = 2e9+100;
const LL INF_LL = (LL)INF*(LL)INF;
const int MOD = 1e9+7;

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

LL modpow(LL a, LL n) {
    LL res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % MOD;
        a = a * a % MOD;
        n >>= 1;
    }
    return res;
}

void Main()
{
    LL h,w;cin>>h>>w;
    LL sh,sw;cin>>sh>>sw;
    LL eh,ew;cin>>eh>>ew;
    sh--;
    eh--;
    sw--;
    ew--;

    VS s(h);
    REP(i,h){
        cin>>s[i];
    }
    
    VVL result(h);
    REP(i,h){
        result[i].resize(w,INF_LL);
    }
    PQ_ASC_VL pq;
    result[sh][sw] = 0;
    pq.push({0,sh,sw});

    while(!pq.empty()){
        LL d = pq.top()[0];
        LL x = pq.top()[1];
        LL y = pq.top()[2];
        pq.pop();

        //REP(i,h){
        //    REP(j,w){
        //        cerr<<result[i][j]<<" ";
        //    }
        //    cerr<<endl;
        //}
        //cerr<<endl;

        if(x == eh && y == ew){
            cout<<d<<endl;
            return;
        }

        VL dx = {1,-1,0,0};
        VL dy = {0,0,1,-1};

        REP(i,4){
            LL nx = x+dx[i];
            LL ny = y+dy[i];
            if(nx < 0 || ny < 0 || nx >= h || ny >= w){
                continue;
            }
            if(s[nx][ny] == '#'){
                continue;
            }
            if(result[nx][ny] <= d){
                continue;
            }
            result[nx][ny] = d;
            pq.push({d,nx,ny});
        }

        //warp
        FOR(i,-2,3){
            FOR(j,-2,3){
                LL nx = x+i;
                LL ny = y+j;
                if(nx < 0 || ny < 0 || nx >= h || ny >= w){
                    continue;
                }
                if(s[nx][ny] == '#'){
                    continue;
                }
                if(result[nx][ny] <= d+1){
                    continue;
                }
                result[nx][ny] = d+1;
                pq.push({d+1,nx,ny});
            }

        }



    }

    cout<<-1<<endl;
       
    
	return;
}

int main()
{
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(15);
	Main();
    return 0;
}

Measured memory_bytes: 12828