#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef int Int;
typedef pair<Int, Int> pii;
typedef pair<Int, double> pid;
typedef pair<double, double> pdd;
typedef pair<Int, pii> pip;
typedef pair<pii, Int> ppi;
typedef pair<double, Int> pdp;
typedef vector<Int> veci;
typedef vector<double> vecd;
typedef vector<int> veci;
typedef vector<ll> vecll;
typedef vector<double> vecd;
typedef vector<pii> vecpii;
typedef vector<ppi> vecppi;
typedef vector<veci> mati;
typedef vector<vecll> matll;
typedef vector<vecd> matd;
#define PB(x) push_back(x)
#define EB(x) emplace_back(x)
#define ALL(x) x.begin(),x.end()
#define SZ(x) (x).size()
#define CLR(x) memset(x,0,sizeof x)
#define pdebug() printf("%d\n",__LINE__)
#define REP(i, a, b) for(int i = (a);i <= (b);i++)
#define FORO(i, n) REP(i,0,(int)n-1)
#define FORI(i, n) REP(i,1,(int)n)
#define FORIT(i, t) for(auto i = t.begin();i != t.end();i++)
#define eps 1e-6
#define sqr(x) ((x)*(x))
#define dist(_a, _b) sqrt(sqr(_a.A-_b.A)+sqr(_a.B-_b.B))
#define norm(_a) sqrt(sqr(_a.A)+sqr(_a.B))
#define DEBUG 1
#if DEBUG
#define DUMP(a) do { std::cout << #a " = " << (a) << ", "; } while(false)
#define DUMPLN(a) do { std::cout << #a " = " << (a) << std::endl; } while(false)
#else
#define DUMP(a)
#define DUMPLN(a)
#endif
template<typename T, typename U>
inline void getMin(T &a, U b) { if (a > b) a = b; }
template<typename T, typename U>
inline void getMax(T &a, U b) { if (a < b) a = b; }
template<typename T>
vector<T> getVector(const int n) { return vector<T>(n); }
template<typename T>
vector<T> getVector(const int n, const T a) { return vector<T>(n, a); }
template<typename T>
vector<T> getEmptyVector() { return vector<T>(); }
template<typename T>
void appendAll(vector<T> &a, vector<T> b) { a.insert(a.end(), b.begin(), b.end()); }
template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
// #define X first
// #define Y second
const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, 1, -1};
const ll MOD = 1000000007;
const int MAXN = 1 << 17;
const int inf = 1 << 27;
const ll llinf = 1LL << 50;
const int NIL = -inf;
int popcount(int x) { return __builtin_popcount(x); }

#define Y first
#define X second
void test_case() {
    int H, W;
    pii C, D;
    cin >> H >> W >> C.Y >> C.X >> D.Y >> D.X;
    C.Y--; C.X--;
    D.Y--; D.X--;
    vector<string> maze(H);
    FORO(i, H) cin >> maze[i];
    mati di(H, veci(W, -1));
    priority_queue<pip, vector<pip>, greater<pip>> que;
    que.push(pip(0, C));
    di[C.Y][C.X] = 0;
    while (!que.empty()) {
        pip cur = que.top();
        que.pop();
        int d = cur.first;
        pii u = cur.second;
        if(di[u.Y][u.X] < d) continue;
        if(u == D) break;
        for(int ry = -2;ry <= 2;ry++) {
            for(int rx = -2;rx <= 2;rx++) {
                int y = u.Y + ry;
                int x = u.X + rx;
                int newd = d + (abs(rx) + abs(ry) > 1);
                if(y < 0 ||  y >= H || x < 0 || x >= W) continue;
                if(maze[y][x] == '#') continue;
                if(di[y][x] == -1 || di[y][x] > newd) {
                    di[y][x] = newd;
                    que.push({newd, pii(y, x)});
                }
            }
        }
    }
    cout << di[D.Y][D.X] << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int T = 1;
    while(T--) {
        test_case();
    }

    return 0;
}


Measured memory_bytes: 8400