using System; using System.Collections.Generic; using System.Linq; using System.IO; using System.Threading; using System.Text; using System.Text.RegularExpressions; using System.Diagnostics; using static util; using P = pair; class Program { static void Main(string[] args) { var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }; var solver = new Solver(sw); // var t = new Thread(solver.solve, 1 << 28); // 256 MB // t.Start(); // t.Join(); solver.solve(); sw.Flush(); } } class Solver { StreamWriter sw; Scan sc; void Prt(string a) => sw.WriteLine(a); void Prt(IEnumerable a) => Prt(string.Join(" ", a)); void Prt(params object[] a) => Prt(string.Join(" ", a)); public Solver(StreamWriter sw) { this.sw = sw; this.sc = new Scan(); } public void solve() { int h, w, ai, aj, bi, bj; sc.Multi(out h, out w, out ai, out aj, out bi, out bj); --ai; --aj; --bi; --bj; var s = new char[h][]; for (int i = 0; i < h; i++) { s[i] = sc.Str.ToCharArray(); } var (d1, c1) = calc(s, ai, aj); var (d2, c2) = calc(s, bi, bj); int d = d1[bi][bj]; if (d == M) { Prt(-1); return; } if (c1[bi][bj] > 1) { Prt(d * 2); return; } for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { if (d1[i][j] + d2[i][j] == d && d1[i][j] > 0 && d2[i][j] > 0) { int c = 0; foreach (var item in adjacents(i, j)) { if (s[item.v1][item.v2] != '#') { ++c; } } if (c > 2) { Prt(d * 2 + 2); return; } } } } for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { if (d1[i][j] + d2[i][j] == d && d1[i][j] > 0 && d2[i][j] > 0) { s[i][j] = '#'; } } } (d1, c1) = calc(s, ai, aj); (d2, c2) = calc(s, bi, bj); if (d1[bi][bj] != M) { Prt(d + d1[bi][bj]); return; } var cc1 = new int[h * w]; var cc2 = new int[h * w]; for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { if (d1[i][j] != M) { ++cc1[d1[i][j]]; } if (d2[i][j] != M) { ++cc2[d2[i][j]]; } } } for (int i = 0; i < h * w; i++) { if (cc1[i] > 1 || cc2[i] > 1) { Prt(d * 2 + i * 4); return; } } Prt(-1); } (int[][], int[][]) calc(char[][] s, int si, int sj) { int h = s.Length; int w = s[0].Length; var dist = new int[h][]; var cnt = new int[h][]; for (int i = 0; i < h; i++) { dist[i] = new int[w]; cnt[i] = new int[w]; for (int j = 0; j < w; j++) { dist[i][j] = M; } } dist[si][sj] = 0; cnt[si][sj] = 1; var q = new Queue

(); q.Enqueue(new P(si, sj)); while (q.Any()) { var p = q.Dequeue(); foreach (var item in p.adjacents()) { if (s[item.v1][item.v2] == '#') continue; if (dist[item.v1][item.v2] == M) { dist[item.v1][item.v2] = dist[p.v1][p.v2] + 1; cnt[item.v1][item.v2] = cnt[p.v1][p.v2]; q.Enqueue(item); } else if (dist[item.v1][item.v2] == dist[p.v1][p.v2] + 1) { cnt[item.v1][item.v2] = Math.Min(cnt[item.v1][item.v2] + cnt[p.v1][p.v2], M); } } } return (dist, cnt); } } class pair : IComparable> { public T v1; public U v2; public pair() : this(default(T), default(U)) {} public pair(T v1, U v2) { this.v1 = v1; this.v2 = v2; } public int CompareTo(pair a) { int c = Comparer.Default.Compare(v1, a.v1); return c != 0 ? c : Comparer.Default.Compare(v2, a.v2); } public override string ToString() => v1 + " " + v2; public void Deconstruct(out T a, out U b) { a = v1; b = v2; } } static class util { public static readonly int M = 1000000007; // public static readonly int M = 998244353; public static readonly long LM = 1L << 60; public static readonly double eps = 1e-11; public static void DBG(string a) => Console.Error.WriteLine(a); public static void DBG(IEnumerable a) => DBG(string.Join(" ", a)); public static void DBG(params object[] a) => DBG(string.Join(" ", a)); public static void Assert(params bool[] conds) { if (conds.Any(x => !x)) throw new Exception(); } public static pair make_pair(T v1, U v2) => new pair(v1, v2); public static int CompareList(IList a, IList b) where T : IComparable { for (int i = 0; i < a.Count && i < b.Count; i++) if (a[i].CompareTo(b[i]) != 0) return a[i].CompareTo(b[i]); return a.Count.CompareTo(b.Count); } public static bool inside(int i, int j, int h, int w) => i >= 0 && i < h && j >= 0 && j < w; public static readonly int[] dd = { 0, 1, 0, -1 }; // static readonly string dstring = "RDLU"; public static IEnumerable

adjacents(int i, int j) => Enumerable.Range(0, dd.Length).Select(k => new P(i + dd[k], j + dd[k ^ 1])); public static IEnumerable

adjacents(int i, int j, int h, int w) => adjacents(i, j).Where(p => inside(p.v1, p.v2, h, w)); public static IEnumerable

adjacents(this P p) => adjacents(p.v1, p.v2); public static IEnumerable

adjacents(this P p, int h, int w) => adjacents(p.v1, p.v2, h, w); public static IEnumerable all_subset(this int p) { for (int i = 0; ; i = i - p & p) { yield return i; if (i == p) break; } } public static Dictionary compress(this IEnumerable a) => a.Distinct().OrderBy(v => v).Select((v, i) => new { v, i }).ToDictionary(p => p.v, p => p.i); public static Dictionary compress(params IEnumerable[] a) => compress(a.SelectMany(x => x)); public static T[] inv(this Dictionary dic) { var res = new T[dic.Count]; foreach (var item in dic) res[item.Value] = item.Key; return res; } public static void swap(ref T a, ref T b) where T : struct { var t = a; a = b; b = t; } public static void swap(this IList a, int i, int j) where T : struct { var t = a[i]; a[i] = a[j]; a[j] = t; } public static T[] copy(this IList a) { var ret = new T[a.Count]; for (int i = 0; i < a.Count; i++) ret[i] = a[i]; return ret; } } class Scan { StreamReader sr; public Scan() { sr = new StreamReader(Console.OpenStandardInput()); } public Scan(string path) { sr = new StreamReader(path); } public int Int => int.Parse(Str); public long Long => long.Parse(Str); public double Double => double.Parse(Str); public string Str => ReadLine.Trim(); public string ReadLine => sr.ReadLine(); public pair Pair() { T a; U b; Multi(out a, out b); return new pair(a, b); } public P P => Pair(); public int[] IntArr => StrArr.Select(int.Parse).ToArray(); public long[] LongArr => StrArr.Select(long.Parse).ToArray(); public double[] DoubleArr => StrArr.Select(double.Parse).ToArray(); public string[] StrArr => Str.Split(new[]{' '}, StringSplitOptions.RemoveEmptyEntries); bool eq() => typeof(T).Equals(typeof(U)); T ct(U a) => (T)Convert.ChangeType(a, typeof(T)); T cv(string s) => eq() ? ct(int.Parse(s)) : eq() ? ct(long.Parse(s)) : eq() ? ct(double.Parse(s)) : eq() ? ct(s[0]) : ct(s); public void Multi(out T a) => a = cv(Str); public void Multi(out T a, out U b) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); } public void Multi(out T a, out U b, out V c) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); } public void Multi(out T a, out U b, out V c, out W d) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); d = cv(ar[3]); } public void Multi(out T a, out U b, out V c, out W d, out X e) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); d = cv(ar[3]); e = cv(ar[4]); } public void Multi(out T a, out U b, out V c, out W d, out X e, out Y f) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); d = cv(ar[3]); e = cv(ar[4]); f = cv(ar[5]); } }