using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

namespace ABC176_D
{
    using static Ex;
    public class D
    {
        public static void Main(string[] args)
        {
            new ABC();
        }
    }

    public class ABC
    {
        int h, w;
        (int, int) st;
        (int, int) goal;
        bool[][] arr;

        int[] vx = { 0, 1, 0, -1 };
        int[] vy = { 1, 0, -1, 0 };

        /// <summary>
        /// # のとき壁であり、.のとき道
        /// 
        /// マス(Ch,Cw) -> (Dh,Dw)まで
        /// 
        /// 移動A：現在いるマスと上下左右に隣接する道のマスへ歩いて移動する。
        /// 移動B：現在いるマスを中心とする5×5の範囲内にある道のマスへワープ魔法で移動する。
        ///
        /// ワープ魔法を使う最小回数
        /// 到達不可能な場合、かわりに -1
        /// </summary>
        public ABC()
        {
            (h, w) = ReadIntArray().ToTpl2();
            st = ReadIntArray().ToTpl2();
            goal = ReadIntArray().ToTpl2();
            arr = new bool[h][];
            for (int i = 0; i < h; i++)
            {
                arr[i] = Read.Select(v => v == '.').ToArray();
            }
            st.Item1--; st.Item2--; goal.Item1--; goal.Item2--;

            var q = new Queue<(int, int, long)>();
            var qq = new Queue<(int, int, long)>();
            q.Enqueue((st.Item1, st.Item2, 0));
            qq.Enqueue((st.Item1, st.Item2, 0));
            while (qq.Any())
            {
                while (q.Any())
                {
                    var now = q.Dequeue();

                    if (now.Item1 == goal.Item1 && now.Item2 == goal.Item2)
                    {
                        now.Item3.Cw();
                        return;
                    }

                    var y = now.Item1;
                    var x = now.Item2;
                    var step = now.Item3;
                    arr[y][x] = false;
                    for (int i = 0; i < 4; i++)
                    {
                        int nx = x + vx[i];
                        int ny = y + vy[i];
                        if ((0 <= nx && nx < w) && (0 <= ny && ny < h) && arr[ny][nx])
                        {
                            arr[ny][nx] = false;
                            q.Enqueue((ny, nx, step));
                            qq.Enqueue((ny, nx, step));
                        }
                    }
                }
                {

                    var now = qq.Dequeue();

                    if (now.Item1 == goal.Item1 && now.Item2 == goal.Item2)
                    {
                        now.Item3.Cw();
                        return;
                    }

                    var y = now.Item1;
                    var x = now.Item2;
                    var step = now.Item3;
                    for (int i = -2; i <= 2; i++)
                        for (int j = -2; j <= 2; j++)
                        {
                            int nx = x + i;
                            int ny = y + j;
                            //if((0 <= nx && nx < w) && (0 <= ny && ny < h)) $" {nx} {ny} {arr[ny][nx]}{ used[ny][nx]}".Cw();
                            if ((0 <= nx && nx < w) && (0 <= ny && ny < h) && arr[ny][nx])
                            {
                                arr[ny][nx] = false;
                                q.Enqueue((ny, nx, step + 1));
                                qq.Enqueue((ny, nx, step + 1));
                            }
                        }
                }
            }
            (-1).Cw();
        }
    }

    public static class Ex
    {
        public static void Cw(this object s) { Console.WriteLine(s); }



        public static bool Mins<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) > 0) { a = b; return true; } return false; }
        public static bool Maxs<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
        public static void Swap<T>(ref T a, ref T b) { var t = b; b = a; a = t; }
        public static void Swap<T>(List<T> list, int i, int j) { T tmp = list[j]; list[j] = list[i]; list[i] = tmp; }

        public static long Lcm(int x, int y) { return x / Gcd(x, y) * y; }
        public static long Gcd(long m, long n) { if (n == 0) return m; return Gcd(n, m % n); }
        public static List<string> FastSort(this List<string> s) { s.Sort(StringComparer.Ordinal); return s.ToList(); }
        public static void yesno(this bool b) { (b ? "yes" : "no").Cw(); }
        public static void YesNo(this bool b) { (b ? "Yes" : "No").Cw(); }
        public static void YESNO(this bool b) { (b ? "YES" : "NO").Cw(); }

        public static string Read { get { return Console.ReadLine().Trim(); } }
        public static int ReadInt { get { return int.Parse(Read); } }
        public static long ReadLong { get { return long.Parse(Read); } }
        public static double ReadDouble { get { return double.Parse(Read); } }
        public static string[] ReadArray() { return Read.Split(' '); }
        public static int[] ReadIntArray() { return Read.Split(' ').Select(int.Parse).ToArray(); }
        public static long[] ReadLongArray() { return Read.Split(' ').Select(long.Parse).ToArray(); }
        public static string[] ReadArray(long N) { var v = new string[N]; for (long i = 0; i < N; ++i) v[i] = Read; return v; }
        public static int[] ReadIntArray(long N) { var v = new int[N]; for (long i = 0; i < N; ++i) v[i] = ReadInt; return v; }
        public static long[] ReadLongArray(long N) { var v = new long[N]; for (long i = 0; i < N; ++i) v[i] = ReadLong; return v; }

        public static (T, T) ToTpl2<T>(this T[] v) { return (v[0], v[1]); }
        public static (T, T, T) ToTpl3<T>(this T[] v) { return (v[0], v[1], v[2]); }
        public static (T, T, T, T) ToTpl4<T>(this T[] v) { return (v[0], v[1], v[2], v[3]); }
        public static (T, T, T, T, T) ToTpl5<T>(this T[] v) { return (v[0], v[1], v[2], v[3], v[4]); }
    }
}


Measured memory_bytes: 42976