#include <iostream>
#include <iosfwd>
#include <iomanip>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <cassert>
#include <cctype>
#include <climits>
#include <vector>
#include <bitset>
#include <set>
#include <queue>
#include <stack>
#include <map>
#include <deque>
#include <string>
#include <list>
#include <iterator>
#include <sstream>
#include <complex>
#include <fstream>
#include <functional>
#include <numeric>
#include <utility>
#include <algorithm>
#include <chrono>
#include <unordered_set>
#include <unordered_map>
#include <random>
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 

using namespace __gnu_pbds;
using namespace std;

template<class T> using OrderedSet = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// MACROS_BEGIN
#define CLEAR() cerr << endl;
#define LET(x, a) __typeof(a) x = a
#define FOREACH(it, v) for (LET(it, (v).begin()); it != (v).end(); ++it)
#define REPEAT(i, n) for (int i = 0; i < (n); ++i)
// MACROS_END

// GENERIC_UTILITIES_BEGIN
// template <class T> inline int size(const T& c) {return (int) c.size();}
inline long long two(int x) {return (1LL << (x));}

vector<string> split(string s, string delim) {
    s += delim[0];
    string tmp;
    vector<string> result;
    for (int i = 0; i < size(s); ++i) {
        if (delim.find(s[i]) == string::npos) {
            tmp.push_back(s[i]);
        }
        else {
            if (tmp != "") result.push_back(tmp);
            tmp.clear();
        }
    }
    return result;
}
// GENERIC_UTILITIES_END

// FAST_IO_BEGIN
// FAST_IO_END

// STANDARD_IO_BEGIN
#ifndef USING_FAST_IO
int readInt() {int N = -1; scanf("%d", &N); return N;}
double readDouble() {double D; scanf("%lf", &D); return D;}
string readString() {char buffer[1 << 20]; scanf("%s", buffer); return buffer;}
long long readLongLong() {long long N = -1; scanf("%lld", &N); return N;}
#endif // NOT DEFINED USING_FAST_IO
// STANDARD_IO_END


// OUTPUT_UTILITIES_BEGIN
template <class A, class B> ostream& operator << (ostream& o, const pair<A, B>& p);
template <class T> ostream& operator << (ostream& o, const vector<T>& v);
template <class A, class B> ostream& operator << (ostream& o, const map<A, B>& m);
template <class T> ostream& operator << (ostream& o, const set<T>& s);
template <class T> ostream& operator << (ostream& o, const queue<T>& q);
template <class T> ostream& operator << (ostream& o, const stack<T>& s);

template <class A, class B> ostream& operator << (ostream& o, const pair<A, B>& p) {
    o << "(" << p.first << "," << p.second << ")"; return o;
}

template <class T> ostream& operator << (ostream& o, const vector<T>& v) {
    o << "{"; bool first = true; FOREACH(it, v) { if (!first) o << ","; first = false; o << *it; } return o << "}";
}

template <class A, class B> ostream& operator << (ostream& o, const map<A, B>& m) {
    o << "{"; bool first = true; FOREACH(it, m) { if (!first) o << ","; first = false; o << *it; } return o << "}";
}

template <class T> ostream& operator << (ostream& o, const set<T>& s) {
    o << "{"; bool first = true; FOREACH(it, s) { if (!first) o << ","; first = false; o << *it; } return o << "}";
}

template <class T> ostream& operator << (ostream& o, const queue<T>& q) {
    o << "{"; bool first = true; queue<T> p = q; while (!p.empty()) { if (!first) o << ","; first = false; o << p.front(); p.pop(); } return o << "}";
}

template <class T> ostream& operator << (ostream& o, const stack<T>& s) {
    o << "{"; bool first = true; stack<T> r = s; while (!r.empty()) { if (!first) o << ","; first = false; o << r.top(); r.pop(); } return o << "}";
}
// OUTPUT_UTILITIES_END

// DEBUGGING_UTILITIES_BEGIN
// DEBUGGING SWITCH
// #define PHOENIX_DEBUG

#ifdef PHOENIX_DEBUG
#define DEBUG(...) __f(__LINE__, #__VA_ARGS__, __VA_ARGS__)

template<typename Arg> void __print(const string& name, Arg&& arg) {
    cerr << "[" << name << ": " << arg << "]" << " ";
}

void __printLine(int line) {
    cerr << "LINE " << line << ": ";
    cerr << boolalpha;    
}

template<typename Arg> void __g(vector<string>& names, int idx, Arg&& arg) {
    __print(names[idx], arg);
}

template<typename Arg, typename... Args> void __g(vector<string>& names, int idx, Arg&& arg, Args&&... args) {
    __g(names, idx, arg); __g(names, idx + 1, args...);
}

template <typename Arg> void __f(int line, const string& name, Arg&& arg) {
    __printLine(line);
    __print(name, arg); CLEAR();
}

template <typename Arg, typename... Args> void __f(int line, const string& _names, Arg&& arg, Args&&... args) {
    __printLine(line);
    vector<string> names = split(_names, ", "); __g(names, 0, arg, args...); CLEAR();
}
#else
#define DEBUG(...)
#endif
// DEBUGGING_UTILITIES_END

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const double epsilon = 1e-8;
const int infinite    = 2000000000; // 2 * 10^9
const long long infiniteLL = 2000000000000000000LL; // 2 * 10^18
const long long modulo = 1000000007;

struct Task {
    int H, W;
    int Ch, Cw, Dh, Dw;
    vector<string> S;
    vector< vector<int> > matrix;
    vector< set<int> > adj;
    vector<int> dist;
    vector<bool> visited;
    int color;

    void addEdge(int u, int v) {
        adj[u].insert(v);
        adj[v].insert(u);
    }

    void readInput() {
        H = readInt(), W = readInt();
        Ch = readInt() - 1, Cw = readInt() - 1;
        Dh = readInt() - 1, Dw = readInt() - 1;
        S.resize(H);
        matrix.resize(H, vector<int> (W, 0));

        for (int i = 0; i < H; ++i) {
            S[i] = readString();
        }

        for (int i = 0; i < H; ++i) {
            for (int j = 0; j < W; ++j) {
                matrix[i][j] = S[i][j] == '#' ? -1 : 0;
            }
        }

        color = 1;

        for (int i = 0; i < H; ++i) {
            for (int j = 0; j < W; ++j) {
                if (matrix[i][j] == 0) {
                    dfs(i, j);
                    ++color;
                }
            }
        }
        DEBUG(matrix);

        adj.resize(color + 1);

        for (int i = 0; i < H; ++i) {
            for (int j = 0; j < W; ++j) {
                for (int x : {i - 2, i - 1, i, i + 1, i + 2}) {
                    for (int y : {j - 2, j - 1, j, j + 1, j + 2}) {
                        if (valid(x, y) && matrix[i][j] != matrix[x][y] && matrix[i][j] != -1 && matrix[x][y] != -1) {
                            int c1 = matrix[i][j], c2 = matrix[x][y];
                            addEdge(c1, c2);
                        }
                    }
                }
            }
        }
        DEBUG(adj);

        bfs(matrix[Ch][Cw]);
        printf("%d\n", dist[matrix[Dh][Dw]]);
    }

    void bfs(int x) {
        dist.resize(size(adj), -1);
        visited.resize(size(adj), false);
        visited[x] = true;
        dist[x] = 0;
        queue<int> q;
        q.push(x);
        DEBUG(x);DEBUG(matrix[Dh][Dw]);

        while (!q.empty()) {
            int u = q.front();
            q.pop();

            for (int v : adj[u]) {
                if (!visited[v]) {
                    visited[v] = true;
                    dist[v] = dist[u] + 1;
                    q.push(v);
                }
            }
        }
        DEBUG(dist);
    }

    bool valid(int r, int c) {
        return r >= 0 && c >= 0 && r < H && c < W;
    }

    void dfs(int i, int j) {
        matrix[i][j] = color;

        for (int x : {i - 1, i, i + 1}) {
            for (int y : {j - 1, j, j + 1}) {
                if (valid(x, y) && matrix[x][y] == 0 && (abs(x - i) + abs(y - j) == 1)) {
                    dfs(x, y);
                }
            }
        }
    }

    void perform() {
        readInput();
        // solve();
    }
};

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    Task task;
    task.perform();

    return 0;
}

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Measured memory_bytes: 33104