#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef double db;
typedef string str;

typedef pair<int,int> pi;
typedef pair<ll,ll> pl;
typedef pair<db,db> pd;

typedef vector<int> vi; 
typedef vector<ll> vl; 
typedef vector<db> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
typedef vector<pd> vpd; 

#define mp make_pair
#define f first
#define s second
#define sz(x) (int)(x).size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend() 
#define rsz resize
#define ins insert 
#define ft front() 
#define bk back()
#define pf push_front 
#define pb push_back
#define eb emplace_back 
#define lb lower_bound 
#define ub upper_bound 

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

const int MX  = 1e3+5; 
const int MOD = 1e9+7; // 998244353;
const ll  INF = 1e18; 
const ld  PI  = acos((ld)-1);

const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1};
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 

template<class T> bool ckmin(T& a, const T& b) { 
	return b < a ? a = b, 1 : 0; 
}
template<class T> bool ckmax(T& a, const T& b) { 
	return a < b ? a = b, 1 : 0; 
} 

constexpr int pct(int x) { return __builtin_popcount(x); } // number of ones 
constexpr int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x)) 
template<class T> T cdiv(T a, T b) { return a/b+!(a<0||a%b == 0); } // division of a by b rounded up, assumes b > 0 

int fstTrue(function<bool(int)> f, int lo, int hi) {
	hi++; assert(lo <= hi); // assuming f is increasing
	while (lo < hi) { // find first index such that f is true 
		int mid = (lo+hi)/2; 
		f(mid) ? hi = mid : lo = mid+1; 
	} 
	return lo;
}

template<class T> void remDup(vector<T>& v) { 
	sort(all(v)); v.erase(unique(all(v)),end(v)); 
}

// DEBUG
void DBG() { cerr << "]" << endl; }
template<class H, class... T> void DBG(H h, T... t) {
	cerr << h; if (sizeof...(t)) cerr << ", ";
	DBG(t...); 
}
#define dbg(...) cerr << "LINE(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)

// FILE I/O
void setIn(str S) { freopen(S.c_str(),"r",stdin); }
void setOut(str S) { freopen(S.c_str(),"w",stdout); }
void setIO(str S = "") {
	ios_base::sync_with_stdio(0); cin.tie(0); // fast I/O
	// cin.exceptions(cin.failbit); 
	// throws exception when do smth illegal
	// ex. try to read letter into int
	if (sz(S)) { setIn(S+".in"), setOut(S+".out"); } // for USACO
}

int N,M;
char arr[MX][MX];
int dist[MX][MX];

bool ok(int x, int y) {
    return x >= 1 && x <= N && y >= 1 && y <= M;
}

int dijkstra(pi st, pi en) {
    priority_queue<pair<int,pi>,vector<pair<int,pi>>,greater<pair<int,pi>>> todo; 
    todo.push({0,st}); dist[st.f][st.s] = 0;
    while(sz(todo)) { 
        auto cur = todo.top(); todo.pop();

        if (cur.s == en) return cur.f;
    
        F0R(i,4) {
            int nx = cur.s.f+xd[i];
            int ny = cur.s.s+yd[i];

            if (!ok(nx,ny) || arr[nx][ny] == '#') continue;
            if (dist[nx][ny] > dist[cur.s.f][cur.s.s]) {
                dist[nx][ny] = dist[cur.s.f][cur.s.s];
                todo.push({dist[nx][ny],{nx,ny}});
            }
        }

        FOR(i,-2,3) {
            FOR(j,-2,3) {
                int nx = cur.s.f+i;
                int ny = cur.s.s+j;

                if (i == 0 && j == 0) continue;
                if (!ok(nx,ny) || arr[nx][ny] == '#') continue;
                if (dist[nx][ny] > dist[cur.s.f][cur.s.s]+1) {
                    dist[nx][ny] = dist[cur.s.f][cur.s.s]+1;
                    todo.push({dist[nx][ny],{nx,ny}});
                }
            }
        }
    }
    return -1;
}

int32_t main() { 
	
    setIO();

    cin >> N >> M;

    pi st,en; cin >> st.f >> st.s >> en.f >> en.s;

    FOR(i,1,N+1) FOR(j,1,M+1) {
        cin >> arr[i][j];
        dist[i][j] = MOD;
    }

    cout << dijkstra(st,en) << "\n";
}

Measured memory_bytes: 8584