#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

struct io_setup{
    io_setup(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

int main(){
    int H, W;
    cin >> H >> W;
    int sx, sy, tx, ty;
    cin >> sx >> sy >> tx >> ty;
    sx--, sy--, tx--, ty--;
    vector<string> S(H);
    rep(i, H) cin >> S[i];

    queue<pii> que;
    vector<vector<int>> d(H, vector<int>(W, inf));
    vector<vector<pii>> pre(H, vector<pii>(W));
    
    que.emplace(sx, sy);
    d[sx][sy] = 0;
    vector<int> dx = {1, 0, -1, 0}, dy = {0, 1, 0, -1};
    vector<vector<bool>> tw(H, vector<bool>(W, false));
    
    while(!que.empty()){
        auto [i, j] = que.front(); que.pop();
        rep(k, 4){
            int ni = i+dx[k], nj = j+dy[k];
            if(S[ni][nj] == '#') continue;
            if(chmin(d[ni][nj], d[i][j]+1)){
                que.emplace(ni, nj);
                pre[ni][nj] = pii(i, j);
            }
            else if(d[ni][nj] == d[i][j]+1){
                tw[ni][nj] = true;
            }
        }
    }
    
    if(d[tx][ty] == inf) {cout << -1 << '\n'; return 0;}
    
    bool flag = false;
    int px = tx, py = ty;
    while(true){
        if(tw[px][py]) {cout << 2*d[tx][ty] << '\n'; return 0;}
        auto[ax, ay] = pre[px][py];
        px = ax, py = ay;
        if(px == sx && py == sy) break;
        int deg = 0;
        rep(k, 4){
            if(S[px+dx[k]][py+dy[k]] == '.') deg++;
        }
        if(deg >= 3) flag = true;
    }
    
    int deg = 0;
    rep(k, 4){
        if(S[sx+dx[k]][sy+dy[k]] == '.') deg++;
    }
    if(deg >= 2) flag = true;
    deg = 0;
    rep(k, 4){
        if(S[tx+dx[k]][ty+dy[k]] == '.') deg++;
    }
    if(deg >= 2) flag = true;
    
    if(!flag) cout << -1 << '\n';
    else cout << d[tx][ty]*2+2 << '\n';
}