#include <bits/stdc++.h>
using namespace std;
typedef long long lint;
typedef vector<lint> vlint;

#define inf 1e+9
#define endl "\n"
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n); i++)
#define rep_rev(i, n) for (int i = n-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()

#define pb push_back
#define eb emplace_back
#define Size(c) (int)(c).size()

#define lb(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define ub(c, x) distance((c).begin(), upper_bound(all(c), (x)))

template <class T> using pq = priority_queue<T>;
template <class T> using pqg = priority_queue<T, vector<T>, greater<T>>;

template <class T, class S> inline bool chmax(T &a, S b) {
    if(a < b) {a = b;return 1;} return 0;
}
template <class T, class S> inline bool chmin(T &a, S b) {
    if(a > b) {a = b;return 1;} return 0;
}
template <class T>
void line(vector<T> &x){for (auto&& xi : x) cin >> xi;}

inline void IN(void){ return;}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){ cin >> first; IN(rest...); return;}

#define INT(...) int __VA_ARGS__; IN (__VA_ARGS__)
#define LINT(...) lint __VA_ARGS__; IN (__VA_ARGS__)
#define STR(...) string __VA_ARGS__; IN(__VA_ARGS__)

template <class T> void UNIQUE(vector<T> &x) {
    sort(all(x)); x.erase(unique(all(x)), x.end());
}
template <class T> void print_vec(T first, T end){
    for (auto i = first; i < end - 1; i++) cout << *i << " ";
    cout << *(end-1) << endl;
}

template<class... T>
void debug_print(T... args){
    vector<lint> tmp = initializer_list<lint>{args...};
    print_vec(all(tmp));
}
template<class T>
void print(T a){ cout << a << endl;}

vector<string> Yes = {"No", "Yes"};
vector<string> YES = {"NO", "YES"};

int ord(char x){ return (int)(x - 'a');}
char chr(lint x){ return (char)(x + (lint)('a'));}
lint mod = 1e9+7;
// lint mod = 

lint sum(vlint a){lint ret = 0; for(auto&& v:a) ret += v; return ret;}
lint vmini(vlint a, lint &index){
    lint ret = LLONG_MAX;
    rep(i, Size(a)){ if (chmin(ret, a[i])) index = i;}
    return ret;
}
lint vmaxi(vlint a, lint &index){
    lint ret = -LLONG_MAX;
    rep(i, Size(a)){ if (chmax(ret, a[i])) index = i;}
    return ret;
}

lint vmin(vlint a){
    lint ret = LLONG_MAX; for (auto && v : a) chmin(ret, v); return ret;
}
lint vmax(vlint a){
    lint ret = -LLONG_MAX; for (auto && v : a) chmax(ret, v); return ret;
}


vlint base_3(int k){
    vlint ret; while (k > 0){ ret.pb(k % 3); k /= 3;} reverse(all(ret)); return ret;
}

int main(){
    INT(h, w);
    LINT(ch, cw, dh, dw);
    ch --; cw --; dh --; dw --;
    vector<string> grid(h); rep(i, h) cin >> grid[i];

    vector<int> dx = {0, 0, 1, -1, };
    vector<int> dy = {1, -1, 0, 0};
    vector<int> dx1 = {0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, -1, -1, -1, -1, -2, -2, -2, -2, -2};
    vector<int> dy1 = {2, -2, 1, 2, -1, -2, 0, 1, 2, -1, -2, 1, 2, -1, -2, 0, 1, 2, -1, -2};
    vector<vlint> visited(h, vlint(w, 0));
    vector<vlint> dist(h, vlint(w, 10000000));
    pqg<vlint> q; q.push({0, ch, cw});
    dist[ch][cw] = 0;
    lint x, y, nx, ny; vlint now;
    while(!q.empty()){
        now = q.top(); q.pop();
        x = now[1]; y = now[2];

        if (visited[x][y]) continue;
        rep(i, 4){
            nx = x + dx[i];
            ny = y + dy[i];
            //print(nx); print(ny);
            if (nx < 0 || nx >= h) continue;
            if (ny < 0 || ny >= w) continue;
            if (grid[nx][ny] == '#') continue;
            if (visited[nx][ny] == 1) continue;
            if (chmin(dist[nx][ny], dist[x][y])){
                q.push({dist[x][y], nx, ny});

            }
        }
        rep(i, 21){
            nx = x + dx1[i];
            ny = y + dy1[i];
            if (nx < 0 || nx >= h) continue;
            if (ny < 0 || ny >= w) continue;

            if (grid[nx][ny] == '#') continue;
            if (visited[nx][ny] == 1) continue;
            if (chmin(dist[nx][ny], dist[x][y]+1)){
                q.push({dist[x][y]+1, nx, ny});

            }
        }
        visited[x][y] = 1;
    }
    if (dist[dh][dw] == 10000000){
        print(-1);
    }
    else print(dist[dh][dw]);
    
}


Measured memory_bytes: 21516