#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
using bint = boost::multiprecision::cpp_int;
using ll = long long;
using pint = pair<int, int>;
using pll = pair<ll, ll>;
#define rep(i,n) for (int i = 0; i < (n); i++)
#define repSE(i,s,n) for (int i = (s); i < (n); i++)
#define rrepSE(i,s,e) for (int i = (s); i > (e); i--)
#define ssort(v) sort(v.begin(), v.end())
#define gsort(v) sort(v.rbegin(), v.rend())
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> bool chmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool chmin(T &m, const T q) { if (q < m) {m = q; return true;} else return false; }
#define DEBUG_PRINT(var) std::cout << #var << " = " << var << "\n";

const int MX = int(1e9);

const int di[] = {-1,0,1,0};
const int dj[] = {0,-1,0,1};

int main()
{
    int h, w, ch, cw, dh, dw;
    cin >> h >> w;
    cin >> ch >> cw; ch --; cw --;
    cin >> dh >> dw; dh --; dw --;
    vector<string> s(h);
    rep(i,h) cin >> s[i];
    vector<vector<int>> dist(h, vector<int>(w,MX));
    deque<pint> que;
    dist[ch][cw] = 0;
    que.emplace_back(ch, cw);
    while (!que.empty()) {
        int ci = que.front().first;
        int cj = que.front().second;
        que.pop_front();
        int d = dist[ci][cj];
        rep(i,4) {
            int ni = ci + di[i], nj = cj + dj[i];
            if (ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
            if (s[ni][nj] == '#') continue;
            if (dist[ni][nj] <= d) continue;
            dist[ni][nj] = d;
            que.emplace_front(ni,nj);
        }
        repSE(i,-2,3) repSE(j,-2,3) {
            int ni = ci + i, nj = cj + j;
            if (ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
            if (s[ni][nj] == '#') continue;
            if (dist[ni][nj] <= d+1) continue;
            dist[ni][nj] = d + 1;
            que.emplace_back(ni,nj);
        }
    }
    cout << (dist[dh][dw] == MX ? -1 : dist[dh][dw]) << "\n";
    return 0;
}


Measured memory_bytes: 9472