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

public class AtCoderA
{
    static void Main()
    {
        var sc = new Scanner();

        long h = sc.NextLong();
        long w = sc.NextLong();
        long ch = sc.NextLong() - 1;
        long cw = sc.NextLong() - 1;
        long dh = sc.NextLong() - 1;
        long dw = sc.NextLong() - 1;

        char[,] map = new char[h, w];
        for (int i = 0; i < h; i++)
        {
            string s = sc.Next();
            for (int j = 0; j < w; j++)
            {
                map[i, j] = s[j];
            }
        }

        long[,] answers = new long[h, w];
        for (int i = 0; i < h; i++)
        {
            for (int j = 0; j < w; j++)
            {
                answers[i, j] = long.MaxValue;
            }
        }

        LinkedList<Tuple<long, long, long>> list = new LinkedList<Tuple<long, long, long>>();
        list.AddFirst(Tuple.Create(ch, cw, (long)0));

        // 4近傍（上、下、左、右）
        int[] hs = new int[] { -1, 1, 0, 0 };
        int[] ws = new int[] { 0, 0, -1, 1 };
        while (list.Count > 0)
        {
            var tupple = list.First();
            var h1 = tupple.Item1;
            var w1 = tupple.Item2;
            var cost = tupple.Item3;
            list.RemoveFirst();

            if (answers[h1, w1] != long.MaxValue)
            {
                continue;
            }

            answers[h1, w1] = cost;

            for (int i = 0; i < 4; i++)
            {
                var h2 = h1 + hs[i];
                var w2 = w1 + ws[i];
                if (h2 < 0 || h2 >= h || w2 < 0 || w2 >= w)
                {
                    continue;
                }
                if (map[h2, w2] == '#')
                {
                    continue;
                }
                if (answers[h2, w2] != long.MaxValue)
                {
                    continue;
                }
                list.AddFirst(Tuple.Create(h2, w2, cost));
            }

            for (int x = -2; x <= 2; x++)
            {
                for (int y = -2; y <= 2; y++)
                {
                    var h2 = h1 + x;
                    var w2 = w1 + y;
                    if (h2 < 0 || h2 >= h || w2 < 0 || w2 >= w)
                    {
                        continue;
                    }
                    if (map[h2, w2] == '#')
                    {
                        continue;
                    }
                    if (answers[h2, w2] != long.MaxValue)
                    {
                        continue;
                    }
                    list.AddLast(Tuple.Create(h2, w2, cost + 1));
                }
            }
        }

        long answer = answers[dh, dw];
        if (answer == long.MaxValue)
        {
            answer = -1;
        }

        Console.WriteLine(answer);
    }

    class Scanner
    {
        private string[] _line;
        private int _index;
        private const char Separator = ' ';

        public Scanner()
        {
            _line = new string[0];
            _index = 0;
        }

        public string Next()
        {
            while (_index >= _line.Length)
            {
                _line = Console.ReadLine().Split(Separator);
                _index = 0;
            }

            return _line[_index++];
        }

        public int NextInt() => int.Parse(Next());
        public long NextLong() => long.Parse(Next());
        public double NextDouble() => double.Parse(Next());
        public decimal NextDecimal() => decimal.Parse(Next());
        public char NextChar() => Next()[0];
        public char[] NextCharArray() => Next().ToCharArray();

        public string[] Array()
        {
            _line = Console.ReadLine().Split(Separator);
            _index = _line.Length;
            return _line;
        }

        public int[] IntArray() => Array().Select(int.Parse).ToArray();
        public long[] LongArray() => Array().Select(long.Parse).ToArray();
        public double[] DoubleArray() => Array().Select(double.Parse).ToArray();
        public decimal[] DecimalArray() => Array().Select(decimal.Parse).ToArray();
    }
}


Measured memory_bytes: 62828