using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Text;
using System.Diagnostics;
using System.Numerics;
using static System.Console;
using static System.Convert;
using static System.Math;
using static Template;
using SC = Scanner;

public partial class Solver
{
    int H, W, Ch, Cw, Dh, Dw;
    public void Solve()
    {
        sc.Make(out H, out W, out Ch, out Cw, out Dh, out Dw);
        var G = sc.Grid(H);
        Cw--; Ch--; Dh--; Dw--;
        var dist = Create(H * W, () => int.MaxValue >> 1);
        var res = Create(H * W, () => int.MaxValue >> 1);
        var seg = new SegmentTree<int>(H * W, 0, (a, b) => dist[a] < dist[b] ? a : b);
        dist[Id(Ch, Cw)] = 0;
        for (int i = 0; i < H * W; i++) seg[i] = i;
        seg.Build();
        while (true)
        {
            int p = seg.dat[1];
            if (dist[p] == int.MaxValue / 2) break;
            res[p] = dist[p];
            dist[p] = int.MaxValue >> 1;
            seg.Update(p, p);
            for (var i = 0; i < gh.Length; i++)
            {
                int nh = p / W + gh[i], nw = gw[i] + p % W;
                int id = Id(nh, nw);
                if (!Inside(nh, nw, H, W) || Min(dist[id],res[id]) <= res[p] || G[nh][nw] == '#') continue;

                dist[id] = res[p];
                seg.Update(id, id);
            }
            for (int i = -2; i <= 2; i++)
                for (int j = -2; j <= 2; j++)
                {
                    int nh = p / W + i, nw = j+ p % W;
                    int id = Id(nh, nw);
                    if (!Inside(nh, nw, H, W) || Min(dist[id],res[id]) <= res[p]+1 || G[nh][nw] == '#') continue;
                    dist[id] = res[p] + 1;
                    seg.Update(id, id);
                }
        }
        if (res[Id(Dh, Dw)] == int.MaxValue >> 1) Fail(-1);
        Console.WriteLine(res[Id(Dh, Dw)]);
    }
    int Id(int h, int w) => h * W + w;
    int[] gh = new[] { 0, 0, 1, -1 }, gw = new[] { 1, -1, 0, 0 };
    public static bool Inside(int h, int w, int H, int W)
        => 0 <= h && h < H && 0 <= w && w < W;
}

public class SegmentTree<T>
{
    public readonly T[] dat;
    protected readonly int sz;
    protected readonly Func<T, T, T> merge;
    protected readonly Func<T, T, T> update;
    protected readonly T id;
    private bool finished = true;
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected int Left(int i)
        => i << 1;
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    protected int Right(int i)
        => (i << 1) | 1;
    public T this[int i]
    {
        get { return dat[i + sz]; }
        set { finished = false; dat[i + sz] = value; }
    }

    public SegmentTree(int N, T id, Func<T, T, T> merge, Func<T, T, T> update = null)
    {
        this.sz = 1;
        while (sz < N) sz <<= 1;
        this.id = id;
        this.merge = merge;
        this.update = update ?? ((T val1, T val2) => val2);
        dat = Create(sz << 1, () => id);
    }

    public void Update(int i, T value)
    {
        i += sz;
        dat[i] = update(dat[i], value);
        while (i > 1)
        {
            i >>= 1;
            dat[i] = merge(dat[Left(i)], dat[Right(i)]);
        }
    }

    public void Build()
    {
        for (int i = sz - 1; i > 0; i--)
            dat[i] = merge(dat[Left(i)], dat[Right(i)]);
        finished = true;
    }

    public virtual T Query(int left, int right)
    {
        if (!finished) throw new Exception("You need to Execute \"Build()\"");
        T l = id, r = id;
        for (left += sz, right += sz; left < right; left >>= 1, right >>= 1)
        {
            if ((left & 1) == 1) l = merge(l, dat[left++]);
            if ((right & 1) == 1) r = merge(dat[--right], r);
        }
        return merge(l, r);
    }

    public int Find(int st, Func<T, bool> check)
    {
        var x = id;
        return Find(st, check, ref x, 1, 0, sz);
    }
    private int Find(int st, Func<T, bool> check, ref T x, int k, int l, int r)
    {
        if (l + 1 == r)
        { x = merge(x, dat[k]); return check(x) ? k - sz : -1; }
        var m = (l + r) >> 1;
        if (m <= st) return Find(st, check, ref x, Right(k), m, r);
        if (st <= l && !check(merge(x, dat[k])))
        { x = merge(x, dat[k]); return -1; }
        var xl = Find(st, check, ref x, Left(k), l, m);
        if (xl >= 0) return xl;
        return Find(st, check, ref x, Right(k), m, r);
    }
}
#region Template
public partial class Solver
{
    public SC sc = new SC();
    static void Main(string[] args)
    {
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        var sol = new Solver();
        int testcase = 1;
        //testcase = sol.sc.Int;
        //var th = new Thread(sol.Solve, 1 << 26);th.Start();th.Join();
        while (testcase-- > 0)
            sol.Solve();
        Console.Out.Flush();
    }
}
public static class Template
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmin<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) > 0) { a = b; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmax<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(ref T a, ref T b) { var t = b; b = a; a = t; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(this IList<T> A, int i, int j) { var t = A[i]; A[i] = A[j]; A[j] = t; }
    public static T[] Create<T>(int n, Func<T> f) { var rt = new T[n]; for (var i = 0; i < rt.Length; ++i) rt[i] = f(); return rt; }
    public static T[] Create<T>(int n, Func<int, T> f) { var rt = new T[n]; for (var i = 0; i < rt.Length; ++i) rt[i] = f(i); return rt; }
    public static void Out<T>(this IList<T> A, out T a) => a = A[0];
    public static void Out<T>(this IList<T> A, out T a, out T b) { a = A[0]; b = A[1]; }
    public static void Out<T>(this IList<T> A, out T a, out T b, out T c) { A.Out(out a, out b); c = A[2]; }
    public static void Out<T>(this IList<T> A, out T a, out T b, out T c, out T d) { A.Out(out a, out b, out c); d = A[3]; }
    public static string Concat<T>(this IEnumerable<T> A, string sp) => string.Join(sp, A);
    public static char ToChar(this int s, char begin = '0') => (char)(s + begin);
    public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> A) => A.OrderBy(v => Guid.NewGuid());
    public static int CompareTo<T>(this T[] A, T[] B, Comparison<T> cmp = null) { cmp = cmp ?? Comparer<T>.Default.Compare; for (var i = 0; i < Min(A.Length, B.Length); i++) { int c = cmp(A[i], B[i]); if (c > 0) return 1; else if (c < 0) return -1; } if (A.Length == B.Length) return 0; if (A.Length > B.Length) return 1; else return -1; }
    public static string ToStr<T>(this T[][] A) => A.Select(a => a.Concat(" ")).Concat("\n");
    public static int ArgMax<T>(this IList<T> A, Comparison<T> cmp = null) { cmp = cmp ?? Comparer<T>.Default.Compare; T max = A[0]; int rt = 0; for (int i = 1; i < A.Count; i++) if (cmp(max, A[i]) < 0) { max = A[i]; rt = i; } return rt; }
    public static T PopBack<T>(this List<T> A) { var v = A[A.Count - 1]; A.RemoveAt(A.Count - 1); return v; }
    public static void Fail<T>(T s) { Console.WriteLine(s); Console.Out.Close(); Environment.Exit(0); }
}
public class Scanner
{
    public string Str => Console.ReadLine().Trim();
    public int Int => int.Parse(Str);
    public long Long => long.Parse(Str);
    public double Double => double.Parse(Str);
    public int[] ArrInt => Str.Split(' ').Select(int.Parse).ToArray();
    public long[] ArrLong => Str.Split(' ').Select(long.Parse).ToArray();
    public char[][] Grid(int n) => Create(n, () => Str.ToCharArray());
    public int[] ArrInt1D(int n) => Create(n, () => Int);
    public long[] ArrLong1D(int n) => Create(n, () => Long);
    public int[][] ArrInt2D(int n) => Create(n, () => ArrInt);
    public long[][] ArrLong2D(int n) => Create(n, () => ArrLong);
    private Queue<string> q = new Queue<string>();
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public T Next<T>() { if (q.Count == 0) foreach (var item in Str.Split(' ')) q.Enqueue(item); return (T)Convert.ChangeType(q.Dequeue(), typeof(T)); }
    public void Make<T1>(out T1 v1) => v1 = Next<T1>();
    public void Make<T1, T2>(out T1 v1, out T2 v2) { v1 = Next<T1>(); v2 = Next<T2>(); }
    public void Make<T1, T2, T3>(out T1 v1, out T2 v2, out T3 v3) { Make(out v1, out v2); v3 = Next<T3>(); }
    public void Make<T1, T2, T3, T4>(out T1 v1, out T2 v2, out T3 v3, out T4 v4) { Make(out v1, out v2, out v3); v4 = Next<T4>(); }
    public void Make<T1, T2, T3, T4, T5>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5) { Make(out v1, out v2, out v3, out v4); v5 = Next<T5>(); }
    public void Make<T1, T2, T3, T4, T5, T6>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5, out T6 v6) { Make(out v1, out v2, out v3, out v4, out v5); v6 = Next<T6>(); }
    public void Make<T1, T2, T3, T4, T5, T6, T7>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5, out T6 v6, out T7 v7) { Make(out v1, out v2, out v3, out v4, out v5, out v6); v7 = Next<T7>(); }
    public (T1, T2) Make<T1, T2>() { Make(out T1 v1, out T2 v2); return (v1, v2); }
    public (T1, T2, T3) Make<T1, T2, T3>() { Make(out T1 v1, out T2 v2, out T3 v3); return (v1, v2, v3); }
    public (T1, T2, T3, T4) Make<T1, T2, T3, T4>() { Make(out T1 v1, out T2 v2, out T3 v3, out T4 v4); return (v1, v2, v3, v4); }
}

#endregion

Measured memory_bytes: 49344