using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Runtime.Serialization.Formatters;
using System.Xml.Schema;

public static class Ex
{
    public static bool IsNullOrEmpty(this string s) { return string.IsNullOrEmpty(s); }
    public static List<string> FastSort(this List<string> s) { s.Sort(StringComparer.OrdinalIgnoreCase); return s.ToList(); }
    public static void yesno(this bool b) { Console.WriteLine(b ? "yes" : "no"); }
    public static void YesNo(this bool b) { Console.WriteLine(b ? "Yes" : "No"); }
    public static void YESNO(this bool b) { Console.WriteLine(b ? "YES" : "NO"); }
    public static int PopCount(this int bits)
    {
        bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);
        bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);
        bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);
        bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);
        return (bits & 0x0000ffff) + (bits >> 16 & 0x0000ffff);
    }
}



partial class Program
{
    public string GetStr() { return Console.ReadLine().Trim(); }
    public char GetChar() { return Console.ReadLine().Trim()[0]; }
    public int GetInt() { return int.Parse(Console.ReadLine().Trim()); }
    public long GetLong() { return long.Parse(Console.ReadLine().Trim()); }
    public double GetDouble() { return double.Parse(Console.ReadLine().Trim()); }
    public string[] GetStrArray() { return Console.ReadLine().Trim().Split(' '); }
    public string[][] GetStrArray(int N)
    {
        var res = new string[N][];
        for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ');
        return res;
    }
    public int[] GetIntArray() { return Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray(); }
    public int[][] GetIntArray(int N)
    {
        var res = new int[N][];
        for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray();
        return res;
    }
    public long[] GetLongArray() { return Console.ReadLine().Trim().Split(' ').Select(long.Parse).ToArray(); }
    public long[][] GetLongArray(int N)
    {
        var res = new long[N][];
        for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ').Select(long.Parse).ToArray();
        return res;
    }
    public char[] GetCharArray() { return Console.ReadLine().Trim().Split(' ').Select(char.Parse).ToArray(); }
    public double[] GetDoubleArray() { return Console.ReadLine().Trim().Split(' ').Select(double.Parse).ToArray(); }
    public double[][] GetDoubleArray(int N)
    {
        var res = new double[N][];
        for (int i = 0; i < N; i++) res[i] = Console.ReadLine().Trim().Split(' ').Select(double.Parse).ToArray();
        return res;
    }
    public char[][] GetGrid(int H)
    {
        var res = new char[H][];
        for (int i = 0; i < H; i++) res[i] = Console.ReadLine().Trim().ToCharArray();
        return res;
    }
    public T[] CreateArray<T>(int N, T value)
    {
        var res = new T[N];
        for (int i = 0; i < N; i++) res[i] = value;
        return res;
    }
    public T[][] CreateArray<T>(int H, int W, T value)
    {
        var res = new T[H][];
        for (int i = 0; i < H; i++)
        {
            res[i] = new T[W];
            for (int j = 0; j < W; j++) res[i][j] = value;
        }
        return res;
    }
    public T[][][] CreateArray<T>(int H, int W, int R, T value)
    {
        var res = new T[H][][];
        for (int i = 0; i < H; i++)
        {
            res[i] = new T[W][];
            for (int j = 0; j < W; j++)
            {
                res[i][j] = new T[R];
                for (int k = 0; k < R; k++) res[i][j][k] = value;
            }
        }
        return res;
    }

    Dictionary<int, List<int>> GetUnweightedAdjacencyList(int N, int M, bool isDirected, bool isNode_0indexed)
    {
        var dic = new Dictionary<int, List<int>>();
        foreach (var e in Enumerable.Range(0, N)) { dic.Add(e, new List<int>()); }
        for (int i = 0; i < M; i++)
        {
            var input = GetIntArray();
            var a = isNode_0indexed ? input[0] : input[0] - 1;
            var b = isNode_0indexed ? input[1] : input[1] - 1;
            dic[a].Add(b);
            if (isDirected == false) dic[b].Add(a);
        }
        return dic;
    }
    Dictionary<int, List<(int, long)>> GetWeightedAdjacencyList(int N, int M, bool isDirected, bool isNode_0indexed)
    {
        var dic = new Dictionary<int, List<(int, long)>>();
        foreach (var e in Enumerable.Range(0, N)) { dic.Add(e, new List<(int, long)>()); }
        for (int i = 0; i < M; i++)
        {
            var input = GetIntArray();
            var a = isNode_0indexed ? input[0] : input[0] - 1;
            var b = isNode_0indexed ? input[1] : input[1] - 1;
            var c = input[2];
            dic[a].Add((b, c));
            if (isDirected == false) dic[b].Add((a, c));
        }
        return dic;
    }

    bool eq<T, U>() => typeof(T).Equals(typeof(U));
    T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
    T cv<T>(string s) => eq<T, int>() ? ct<T, int>(int.Parse(s))
                       : eq<T, long>() ? ct<T, long>(long.Parse(s))
                       : eq<T, double>() ? ct<T, double>(double.Parse(s))
                       : eq<T, char>() ? ct<T, char>(s[0])
                                         : ct<T, string>(s);
    void Multi<T>(out T a) => a = cv<T>(GetStr());
    void Multi<T, U>(out T a, out U b)
    {
        var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]);
    }
    void Multi<T, U, V>(out T a, out U b, out V c)
    {
        var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]);
    }
    void Multi<T, U, V, W>(out T a, out U b, out V c, out W d)
    {
        var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]);
    }
    void Multi<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e)
    {
        var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]);
    }
    void Multi<T, U, V, W, X, Y>(out T a, out U b, out V c, out W d, out X e, out Y f)
    {
        var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]); f = cv<Y>(ar[5]);
    }

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

class Pair : IComparable<Pair>
{
    public Pair(int _node, long _cost)
    {
        node = _node; cost = _cost;
    }
    public int node;
    public long cost;
    public int CompareTo(Pair p)
    {
        return p.cost > cost ? 1 : -1;
    }
}

class Comparable : IComparable<Comparable>
{
    public Comparable(int x, int id)
    {
        X = x;
        Id = id;
    }

    public int X;
    public int Id;
    public int CompareTo(Comparable c)
    {
        return X >= c.X ? -1 : 1;
    }
}

class Comparer<T> : IComparer<T>
{
    public int Compare(T t1, T t2)
    {
        return 1;
    }
}





partial class Program
{
    static void Main()
    {
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        new Program().Solve();
        Console.Out.Flush();
        Console.Read();
    }

    public void Solve()
    {
        int H; int W;
        Multi(out H, out W);

        int sy, sx;
        Multi(out sy, out sx);
        sy--; sx--;
        var spos = sy * W + sx;

        int gy, gx;
        Multi(out gy, out gx);
        gy--; gx--;
        var gpos = gy * W + gx;

        var map = GetGrid(H);

        var G = new Dictionary<int, List<(int to, int length)>>();
        for (int y = 0; y < H; y++)
        {
            for (int x = 0; x < W; x++)
            {
                if (map[y][x] == '.') G.Add(y * W + x, new List<(int to, int length)>());
            }
        }

        int pos, npos, nx, ny, heavy;

        var uf = new UnionFind(H * W);

        for (int y = 0; y < H; y++)
        {
            for (int x = 0; x < W; x++)
            {
                if (map[y][x] == '#') continue;
                pos = y * W + x;
                for (int i = 0; i < 4; i++)
                {
                    ny = y + dy[i];
                    nx = x + dx[i];
                    if (ny < 0 || H <= ny || nx < 0 || W <= nx) continue;
                    if (map[ny][nx] == '#') continue;
                    npos = ny * W + nx;
                    uf.Union(pos, ny * W + nx);
                    G[pos].Add((npos, 0));
                    G[npos].Add((pos, 0));
                }
            }
        }

        for (int y = 0; y < H; y++)
        {
            for (int x = 0; x < W; x++)
            {
                if (map[y][x] == '#') continue;
                pos = y * W + x;
                for (int dy = 0; dy <= 2; dy++)
                {
                    ny = y + dy;
                    if (H <= ny) break;
                    for (int dx = -2; dx <= 2; dx++)
                    {
                        if (dy == 0 && dx <= 0) continue;
                        nx = x + dx;
                        if (nx < 0 || W <= nx) continue;
                        if (map[ny][nx] == '#') continue;
                        npos = ny * W + nx;
                        if (uf.Same(pos, npos)) continue;
                        G[pos].Add((npos, 1));
                        G[npos].Add((pos, 1));
                    }
                }
            }
        }

        var dist = CreateArray(H * W, -1);
        var deque = new LinkedList<(int node, int cost)>();

        dist[spos] = 0;
        deque.AddFirst((spos, 0));
        while (deque.Count() > 0)
        {
            var now = deque.First();
            if (now.node == gpos)
            {
                Console.WriteLine(dist[gpos]);
                return;
            }
            deque.RemoveFirst();
            if (dist[now.node] < now.cost) continue;
            foreach (var next in G[now.node])
            {
                var alt = now.cost + next.length;
                if (dist[next.to] != -1 && alt >= dist[next.to]) continue;
                dist[next.to] = alt;
                if (next.length == 1) deque.AddLast((next.to, alt));
                else deque.AddFirst((next.to, alt));
            }
        }
        Console.WriteLine(-1);
    }

    class UnionFind
    {
        int[] parents;
        public UnionFind(int n)
        {
            parents = new int[n];
            for (int i = 0; i < n; i++)
            {
                parents[i] = -1;
            }
        }

        public int Find(int x)
        {
            if (parents[x] < 0) return x;
            return parents[x] = Find(parents[x]);
        }

        public int Size(int x)
        {
            return -parents[Find(x)];
        }

        public bool Same(int x, int y)
        {
            return Find(x) == Find(y);
        }

        public bool Union(int x, int y)
        {
            x = Find(x);
            y = Find(y);
            if (x == y) return false;

            if (Size(x) < Size(y))
            {
                var tmp = x;
                x = y;
                y = tmp;
            }
            parents[x] += parents[y];
            parents[y] = x;
            return true;
        }
    }
}



Measured memory_bytes: 194484