#include <bits/stdc++.h>   
#define rep(i, n) for(long long int i = 0; i < n; i++)
#define _rep(i, m, n) for(long long int i = m; i < n; i++)
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
     
ll gcd(ll A, ll B){
    if(B == 0)return A;
    return gcd(B, A % B);
}
ll lcm(ll A, ll B){
    return A * B / gcd(A, B);
}
template <typename T>
T pow(T a, ll n, T e = 1) {
    T ret = e;
    while (n) {
        if (n & 1) ret *= a;
        a *= a;
        n >>= 1;
    }
    return ret;
}
 
template <int mod>
struct ModInt {
    int x;
    ModInt() : x(0) {}
    ModInt(long long x_) {
        if ((x = x_ % mod + mod) >= mod) x -= mod;
    }
    ModInt& operator+=(ModInt rhs) {
        if ((x += rhs.x) >= mod) x -= mod;
        return *this;
    }
    ModInt& operator-=(ModInt rhs) {
        if ((x -= rhs.x) < 0) x += mod;
        return *this;
    }
    ModInt& operator*=(ModInt rhs) {
        x = (unsigned long long)x * rhs.x % mod;
        return *this;
    }
    ModInt& operator/=(ModInt rhs) {
        x = (unsigned long long)x * rhs.inv().x % mod;
        return *this;
    }
 
    ModInt operator-() const { return -x < 0 ? mod - x : -x; }
    ModInt operator+(ModInt rhs) const { return ModInt(*this) += rhs; }
    ModInt operator-(ModInt rhs) const { return ModInt(*this) -= rhs; }
    ModInt operator*(ModInt rhs) const { return ModInt(*this) *= rhs; }
    ModInt operator/(ModInt rhs) const { return ModInt(*this) /= rhs; }
    bool operator==(ModInt rhs) const { return x == rhs.x; }
    bool operator!=(ModInt rhs) const { return x != rhs.x; }
    ModInt inv() const { return pow(*this, mod - 2); }
 
    friend ostream& operator<<(ostream& s, ModInt<mod> a) {
        s << a.x;
        return s;
    }
    friend istream& operator>>(istream& s, ModInt<mod>& a) {
        s >> a.x;
        return s;
    }
};
 
using mint = ModInt<1000000007>;
using Graph = vector<vector<int>>;
Graph G;
/*------------------------------------------------------------------*/
int h, w;
char s[1010][1010];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> h >> w;
    int ch, cw, dh, dw; cin >> ch >> cw >> dh >> dw;
    ch--, cw--, dh--, dw--;
    rep(i, h)rep(j, w) cin >> s[i][j];

    int INF = 1e8;
    
    deque<pair<int,int>> dq;
    dq.push_back({ch, cw});
    vector<vector<int>> dist(h, vector<int>(w, INF));
    dist[ch][cw] = 0;

    while(!dq.empty()){
        int x = dq.front().first;
        int y = dq.front().second;
        dq.pop_front();

        for(int i = -2; i <= 2; i++){
            for(int j = -2; j <= 2; j++){
                int nx = x + i;
                int ny = y + j;
                if(nx < 0 or nx >= h or ny < 0 or ny >= w) continue;
                if(s[nx][ny] == '#') continue;
                if(i == 0 and j == 0) continue;
                if(abs(i) + abs(j) <= 1 and dist[x][y] < dist[nx][ny]){
                    dist[nx][ny] = dist[x][y];
                    dq.push_front({nx, ny});
                }
                if(dist[x][y] + 1 < dist[nx][ny]){
                    dist[nx][ny] = dist[x][y] + 1;
                    dq.push_back({nx, ny});
                }
            }
        }
    }
    if(dist[dh][dw] < INF) cout << dist[dh][dw] << endl;
    else cout << -1 << endl;
}

Measured memory_bytes: 8464