using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Net;
using System.Numerics;
using System.Reflection.Metadata;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics.X86;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;

namespace AtCoder
{
	public class Program
	{
		static void Main()
		{
			var cin = new Scanner();
			int h = cin.Int();
			int w = cin.Int();
			int ch = cin.Int() - 1;
			int cw = cin.Int() - 1;
			int dh = cin.Int() - 1;
			int dw = cin.Int() - 1;
			var s = new string[h];
			for (int i = 0; i < h; i++) {
				s[i] = cin.Next();
			}

			var d = Helper.Array2(h, w, (i, j) => int.MaxValue);
			d[ch, cw] = 0;
			var q = new Deque<(int i, int j, int n)>();
			q.PushFront((ch, cw, 0));
			while (q.Count > 0) {
				var cur = q.PopFront();
				if (d[cur.i, cur.j] < cur.n) {
					continue;
				}

				for (int i = -2; i <= 2; i++) {
					for (int j = -2; j <= 2; j++) {
						if (i == 0 && j == 0) {
							continue;
						}

						int ni = cur.i + i;
						int nj = cur.j + j;
						if (ni < 0 || ni >= h || nj < 0 || nj >= w) {
							continue;
						}

						if (s[ni][nj] != '#') {
							if ((i == 0 && j == -1)
								|| (i == 0 && j == 1)
								|| (i == -1 && j == 0)
								|| (i == 1 && j == 0)) {
								int nd = cur.n;
								if (d[ni, nj] > nd) {
									d[ni, nj] = nd;
									q.PushFront((ni, nj, nd));
								}
							} else {
								int nd = cur.n + 1;
								if (d[ni, nj] > nd) {
									d[ni, nj] = nd;
									q.PushBack((ni, nj, nd));
								}
							}
						}
					}
				}
			}

			int ans = d[dh, dw];
			if (ans == int.MaxValue) {
				ans = -1;
			}

			Console.WriteLine(ans);
		}
	}

	public class Deque<T> : IEnumerable<T>
	{
		private int capacity_;
		private T[] ringBuffer_;
		private int front_;
		private int back_;

		public int Count { get; private set; } = 0;

		public T this[int index]
		{
			get
			{
				return ringBuffer_[(index + front_) % capacity_];
			}
		}

		public Deque() : this(1024) { }
		public Deque(int capacity)
		{
			if (capacity == 0) {
				capacity = 1024;
			}

			capacity_ = capacity;
			ringBuffer_ = new T[capacity];
			front_ = 0;
			back_ = -1;
		}

		public void PushFront(T item)
		{
			if (Count == capacity_) {
				Extend(capacity_ * 2);
			}

			int index = (front_ + capacity_ - 1) % capacity_;
			ringBuffer_[index] = item;
			front_ = index;

			Count++;
		}

		public void PushBack(T item)
		{
			if (Count == capacity_) {
				Extend(capacity_ * 2);
			}

			int index = (back_ + 1) % capacity_;
			ringBuffer_[index] = item;
			back_ = index;

			Count++;
		}

		public T PopFront()
		{
			if (Count == 0) {
				return default;
			}

			T ret = ringBuffer_[front_];
			front_ = (front_ + 1) % capacity_; ;
			Count--;

			return ret;
		}

		public T PopBack()
		{
			if (Count == 0) {
				return default;
			}

			T ret = ringBuffer_[back_];
			back_ = (back_ + capacity_ - 1) % capacity_; ;
			Count--;

			return ret;
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		private void Extend(int newSize)
		{
			var newBuffer = new T[newSize];
			if (Count > 0) {
				if (front_ <= back_) {
					Array.Copy(ringBuffer_, front_, newBuffer, 0, Count);
				} else {
					int prevLength = ringBuffer_.Length - front_;
					Array.Copy(ringBuffer_, front_, newBuffer, 0, prevLength);
					Array.Copy(ringBuffer_, 0, newBuffer, prevLength, back_ + 1);
				}
			}

			ringBuffer_ = newBuffer;
			capacity_ = newSize;
			front_ = 0;
			back_ = Count - 1;
		}

		public IEnumerator<T> GetEnumerator()
		{
			for (int i = 0; i < Count; i++) {
				yield return this[i];
			}
		}

		IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
	}

	public class HashMap<TKey, TValue> : Dictionary<TKey, TValue>
	{
		private readonly Func<TKey, TValue> initialzier_;
		public HashMap(Func<TKey, TValue> initialzier)
			: base()
		{
			initialzier_ = initialzier;
		}

		public HashMap(Func<TKey, TValue> initialzier, int capacity)
			: base(capacity)
		{
			initialzier_ = initialzier;
		}

		new public TValue this[TKey key]
		{
			get
			{
				if (ContainsKey(key) == false) {
					base[key] = initialzier_(key);
				}

				return base[key];
			}

			set { base[key] = value; }
		}
	}

	public static class Helper
	{
		public static void UpdateMin<T>(ref T target, T value) where T : IComparable<T>
			=> target = target.CompareTo(value) > 0 ? value : target;

		public static void UpdateMin<T>(ref T target, T value, Action<T> onUpdated) where T : IComparable<T>
		{
			if (target.CompareTo(value) > 0) {
				target = value;
				onUpdated(value);
			}
		}

		public static void UpdateMax<T>(ref T target, T value) where T : IComparable<T>
			=> target = target.CompareTo(value) < 0 ? value : target;
		public static void UpdateMax<T>(ref T target, T value, Action<T> onUpdated) where T : IComparable<T>
		{
			if (target.CompareTo(value) < 0) {
				target = value;
				onUpdated(value);
			}
		}

		public static T[] Array<T>(int n, Func<int, T> init)
			=> Enumerable.Range(0, n).Select(x => init(x)).ToArray();
		public static List<T> List<T>(int n, Func<int, T> init)
			=> Enumerable.Range(0, n).Select(x => init(x)).ToList();
		public static T[,] Array2<T>(int n, int m, T init)
		{
			var array = new T[n, m];
			for (int i = 0; i < n; i++) {
				for (int j = 0; j < m; j++) {
					array[i, j] = init;
				}
			}

			return array;
		}

		public static T[,] Array2<T>(int n, int m, Func<int, int, T> initializer)
		{
			var array = new T[n, m];
			for (int i = 0; i < n; i++) {
				for (int j = 0; j < m; j++) {
					array[i, j] = initializer(i, j);
				}
			}

			return array;
		}

		public static T[,,] Array3<T>(int n1, int n2, int n3, T init)
		{
			var array = new T[n1, n2, n3];
			for (int i1 = 0; i1 < n1; i1++) {
				for (int i2 = 0; i2 < n2; i2++) {
					for (int i3 = 0; i3 < n3; i3++) {
						array[i1, i2, i3] = init;
					}
				}
			}

			return array;
		}

		public static T[,,,] Array4<T>(int n1, int n2, int n3, int n4, T init)
		{
			var array = new T[n1, n2, n3, n4];
			for (int i1 = 0; i1 < n1; i1++) {
				for (int i2 = 0; i2 < n2; i2++) {
					for (int i3 = 0; i3 < n3; i3++) {
						for (int i4 = 0; i4 < n4; i4++) {
							array[i1, i2, i3, i4] = init;
						}
					}
				}
			}

			return array;
		}

		private static readonly int[] delta4_ = { 1, 0, -1, 0, 1 };
		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		public static void DoAt4(int i, int j, int imax, int jmax, Action<int, int> action)
		{
			for (int dn = 0; dn < 4; dn++) {
				int d4i = i + delta4_[dn];
				int d4j = j + delta4_[dn + 1];
				if ((uint)d4i < (uint)imax && (uint)d4j < (uint)jmax) {
					action(d4i, d4j);
				}
			}
		}

		private static readonly int[] delta8_ = { 1, 0, -1, 0, 1, 1, -1, -1, 1 };
		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		public static void DoAt8(int i, int j, int imax, int jmax, Action<int, int> action)
		{
			for (int dn = 0; dn < 8; dn++) {
				int d8i = i + delta8_[dn];
				int d8j = j + delta8_[dn + 1];
				if ((uint)d8i < (uint)imax && (uint)d8j < (uint)jmax) {
					action(d8i, d8j);
				}
			}
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		public static void ForEachSubBit(int bit, Action<int> action)
		{
			for (int sub = bit; sub >= 0; sub--) {
				sub &= bit;
				action(sub);
			}
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		public static string Reverse(string src)
		{
			var chars = src.ToCharArray();
			for (int i = 0, j = chars.Length - 1; i < j; i++, j--) {
				var tmp = chars[i];
				chars[i] = chars[j];
				chars[j] = tmp;
			}
			return new string(chars);
		}
	}

	public class Scanner
	{
		private readonly char[] delimiter_ = new char[] { ' ' };
		private readonly string filePath_;
		private readonly Func<string> reader_;
		private string[] buf_;
		private int index_;

		public Scanner(string file = "")
		{
			if (string.IsNullOrWhiteSpace(file)) {
				reader_ = Console.ReadLine;
			} else {
				filePath_ = file;
				var fs = new StreamReader(file);
				reader_ = fs.ReadLine;
			}
			buf_ = new string[0];
			index_ = 0;
		}

		public string NextLine() => reader_();
		public string Next()
		{
			if (index_ < buf_.Length) {
				return buf_[index_++];
			}

			string st = reader_();
			while (st == "") {
				st = reader_();
			}

			buf_ = st.Split(delimiter_, StringSplitOptions.RemoveEmptyEntries);
			if (buf_.Length == 0) {
				return Next();
			}

			index_ = 0;
			return buf_[index_++];
		}

		public int Int() => int.Parse(Next());
		public long Long() => long.Parse(Next());
		public double Double() => double.Parse(Next());

		public int[] ArrayInt(int N, int add = 0)
		{
			int[] Array = new int[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Int() + add;
			}
			return Array;
		}

		public long[] ArrayLong(int N, long add = 0)
		{
			long[] Array = new long[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Long() + add;
			}
			return Array;
		}

		public double[] ArrayDouble(int N, double add = 0)
		{
			double[] Array = new double[N];
			for (int i = 0; i < N; i++) {
				Array[i] = Double() + add;
			}
			return Array;
		}

		public void Save(string text)
		{
			if (string.IsNullOrWhiteSpace(filePath_)) {
				return;
			}

			File.WriteAllText(filePath_ + "_output.txt", text);
		}
	}

	public static class Extensions
	{
		public static string Join<T>(this IEnumerable<T> values, string separator = "")
			=> string.Join(separator, values);
	}
}


Measured memory_bytes: 34636