#include <bits/stdc++.h>
 
using namespace std;
 
template <typename A, typename B>
string to_string(pair<A, B> p);
 
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
 
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
 
string to_string(const string& s) {
  return '"' + s + '"';
}
 
string to_string(const char* s) {
  return to_string((string) s);
}
 
string to_string(bool b) {
  return (b ? "true" : "false");
}
 
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
 
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
 
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
 
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
 
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}
 
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
 
void debug_out() { cerr << endl; }
 
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
 
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#endif


typedef long long ll; 
typedef pair<int, int> pii;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
typedef long double ld;
 
#define mp make_pair
#define pb push_back
#define pf push_front
#define all(a) a.begin(), a.end()
#define S second
#define F first
#define PI 3.14159265358979323846

ll sqr(ll n) {
    return n*n;
}

ll binpow(ll a, ll n) {
    if (n == 0)
        return 1;
    if (n % 2 != 0) return (binpow(a, n-1)*a); else {
        ll b = binpow(a, n/2);
        return (b*b);
    }
}

int gcd(int a, int b) {
    return b ? gcd(b, a % b) : a;
}

int lcm(int a, int b) {
    return a / gcd(a, b) * b;
}

const int N = 1005;
char g[N][N], vis[N][N];
int d[N][N];
int h, w, ch, dh, cw, dw;

int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, 1, -1};

void solve() {
    cin >> h >> w >> ch >> dh >> cw >> dw;
    ch--, dh--, cw--, dw--;

    for (int i = 0; i < h; i++)
        for (int j = 0; j < w; j++)
            cin >> g[i][j];

    memset(d, -1, sizeof d);
    deque<pii> q;

    q.pf({ch, dh});
    d[ch][dh] = 0;
    while (!q.empty()) {
        pii t = q.front();
        q.pop_front();

        if (vis[t.F][t.S]) continue;
        vis[t.F][t.S] = true;
        for (int i = 0; i < 4; i++) {
            int x = t.F + dx[i], y = t.S + dy[i];

            if (x < 0 || x >= h || y < 0 || y >= w) continue;
            if (g[x][y] == '#') continue;

            if (d[x][y] == -1 || d[t.F][t.S] < d[x][y]) {
                d[x][y] = d[t.F][t.S];
                q.pf({x, y});
            }
        }

        for (int i = -2; i < 3; i++)
            for (int j = -2; j < 3; j++) {
                int x = t.F + i, y = t.S + j;

                if (x < 0 || x >= h || y < 0 || y >= w) continue;
                if (g[x][y] == '#') continue;

                if (d[x][y] == -1 || d[t.F][t.S] + 1 < d[x][y]) {
                    d[x][y] = d[t.F][t.S] + 1;
                    q.pb({x, y});
                }
            }
    }
    cout << d[cw][dw] << endl;
}

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

    int t = 1;
    //cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}

Measured memory_bytes: 9544