using A; using System.Buffers; using System.Collections; using System.Diagnostics; using System.Numerics; using System.Runtime.CompilerServices; using static A.InputUtility; class Program { static void Main() { using Output output = new(false); InputNewLine(); var (h, w) = (NextInt32, NextInt32); int[][] a = new int[h][]; for (int i = 0; i < a.Length; i++) { InputNewLine(); a[i] = GetInt32Array(); } int res = 0; var vec = new (int y, int x)[] { (1, 0), (0, 1), (-1, 0), (0, -1), }; int[][] visited = new int[h][]; for (int i = 0; i < visited.Length; i++) { visited[i] = Enumerable.Repeat(-1, w).ToArray(); } PriorityQueue<(int y, int x), int> C = new(); C.Enqueue((0, 0), 0); PriorityQueue<(int y, int x), int> D = new(); D.Enqueue((h - 1, w - 1), 0); for (int i = 0; i < h * w + 2; i++) { if (i % 2 == 0) { while (C.Count > 0 && C.Dequeue() is (int y, int x)) { if (visited[y][x] == 0) { continue; } visited[y][x] = 0; foreach (var (vy, vx) in vec) { var ny = y + vy; var nx = x + vx; if (0 > ny || ny >= h || 0 > nx || nx >= w) { continue; } if (visited[ny][nx] == 1) { Console.WriteLine(i - 1); return; } if (visited[ny][nx] != -1) { continue; } C.Enqueue((ny, nx), a[ny][nx]); } break; } } else { while (D.Count > 0 && D.Dequeue() is (int y, int x)) { if (visited[y][x] == 1) { continue; } visited[y][x] = 1; foreach (var (vy, vx) in vec) { var ny = y + vy; var nx = x + vx; if (0 > ny || ny >= h || 0 > nx || nx >= w) { continue; } if (visited[ny][nx] == 0) { Console.WriteLine(i - 1); return; } if (visited[ny][nx] != -1) { continue; } D.Enqueue((ny, nx), a[ny][nx]); } break; } } } foreach (var row in visited) { Console.WriteLine(string.Join(' ', row)); } } } namespace A { public static class InputUtility { private static string[]? s_inputs; private static string? s_raw; private static int s_index = 0; private static void Init() => s_index = 0; public static int NextInt32 => int.Parse(s_inputs![s_index++]!); public static uint NextUInt32 => uint.Parse(s_inputs![s_index++]!); public static long NextInt64 => long.Parse(s_inputs![s_index++]!); public static ulong NextUInt64 => ulong.Parse(s_inputs![s_index++]!); public static string NextString => s_inputs![s_index++]; public static char NextChar => s_inputs![s_index++][0]; public static decimal NextDecimal => decimal.Parse(s_inputs![s_index++]!); public static BigInteger NextBigInteger => BigInteger.Parse(s_inputs![s_index++]!); public static int[] GetInt32Array() => s_inputs!.Select(int.Parse).ToArray(); public static long[] GetInt64Array() => s_inputs!.Select(long.Parse).ToArray(); public static string[] GetStringArray() => s_inputs!; public static string GetRawString() => s_raw!; #if DEBUG private static TextReader? s_textReader; public static void SetSource(string path) => s_textReader = new StringReader(File.ReadAllText(path)); #endif public static bool InputNewLine() { #if DEBUG if (s_textReader is TextReader sr) { Init(); s_raw = sr.ReadLine()!; s_inputs = s_raw.Split(' ', StringSplitOptions.RemoveEmptyEntries); return true; } #endif Init(); s_raw = Console.ReadLine()!; s_inputs = s_raw.Split(' ', StringSplitOptions.RemoveEmptyEntries); return true; } } public static class CombinationFunction { public static void PartedRotate(T[] a, int first1, int last1, int first2, int last2) { if (first1 == last1 || first2 == last2) return; int next = first2; while (first1 != next) { Swap(a, first1++, next++); if (first1 == last1) first1 = first2; if (next == last2) { next = first2; } else if (first1 == first2) { first2 = next; } } } public static bool NextCombinationImp(T[] a, int first1, int last1, int first2, int last2) where T : IComparable { if (first1 == last1 || first2 == last2) return false; int target = last1 - 1; int lastElem = last2 - 1; while (target != first1 && !(a[target].CompareTo(a[lastElem]) < 0)) target--; if (target == first1 && !(a[target].CompareTo(a[lastElem]) < 0)) { PartedRotate(a, first1, last1, first2, last2); return false; } int next = first2; while (!(a[target].CompareTo(a[next]) < 0)) next++; Swap(a, target++, next++); PartedRotate(a, target, last1, next, last2); return true; } public static bool NextCombination(T[] a, int first, int mid, int last) where T : IComparable => NextCombinationImp(a, first, mid, mid, last); public static bool PrevCombination(T[] a, int first, int mid, int last) where T : IComparable => NextCombinationImp(a, mid, last, first, mid); public static void Swap(T[] a, int i, int j) => (a[i], a[j]) = (a[j], a[i]); } public static class PermutationFunction { public static bool NextPermutation(T[] a) where T : IComparable { int n = a.Length; int i = n - 2; while (i >= 0 && a[i].CompareTo(a[i + 1]) >= 0) { i--; } if (i < 0) { return false; } int j = n - 1; while (a[j].CompareTo(a[i]) <= 0) { j--; } (a[i], a[j]) = (a[j], a[i]); Array.Reverse(a, i + 1, n - i - 1); return true; } public static bool NextPermutation(Span a) where T : IComparable { int n = a.Length; int i = n - 2; while (i >= 0 && a[i].CompareTo(a[i + 1]) >= 0) { i--; } if (i < 0) { return false; } int j = n - 1; while (a[j].CompareTo(a[i]) <= 0) { j--; } (a[i], a[j]) = (a[j], a[i]); a.Slice(i + 1, n - i - 1).Reverse(); return true; } } public readonly struct Output : IDisposable { private readonly StreamWriter _sw; #if DEBUG public Output(string path) { var fs = new FileStream(path, FileMode.Create, FileAccess.Write); _sw = new StreamWriter(fs); Console.SetOut(_sw); } #endif public Output(bool autoFlush) { _sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = autoFlush }; Console.SetOut(_sw); } public void Dispose() { _sw.Dispose(); } [MethodImpl(MethodImplOptions.AggressiveInlining)] internal void Flush() { _sw.Flush(); } } public static class ArrayExtensions { public static void Swap(this T[] array, int i, int j) => (array[i], array[j]) = (array[j], array[i]); public static int LowerBound(this T[] a, T target) where T : IComparable { int ok = a.Length; int ng = -1; while (Math.Abs(ok - ng) > 1 && (ok + ng) / 2 is int mid) (ok, ng) = a[mid].CompareTo(target) >= 0 ? (mid, ng) : (ok, mid); return ok; } public static int UpperBound(this T[] a, T target) where T : IComparable { int ok = a.Length; int ng = -1; while (Math.Abs(ok - ng) > 1 && (ok + ng) / 2 is int mid) (ok, ng) = a[mid].CompareTo(target) > 0 ? (mid, ng) : (ok, mid); return ok; } public struct IndexedEnumerable : IEnumerable<(T item, int index)> { private readonly T[] _a; private readonly int _startIndex; public IndexedEnumerable(T[] a, int startIndex = 0) { _a = a; _startIndex = startIndex; } public readonly IndexedEnumerator GetEnumerator() => new IndexedEnumerator(_a, _startIndex); IEnumerator IEnumerable.GetEnumerator() => GetEnumerator(); IEnumerator<(T item, int index)> IEnumerable<(T item, int index)>.GetEnumerator() => GetEnumerator(); } public struct IndexedEnumerator : IEnumerator<(T item, int index)> { public readonly (T item, int index) Current => (_a[_index], _index + _startIndex); private int _index; private int _startIndex; private T[] _a; public IndexedEnumerator(T[] a, int startIndex) { _index = -1; _a = a; _startIndex = startIndex; } public bool MoveNext() => ++_index < _a.Length; readonly object IEnumerator.Current => Current; public readonly void Dispose() { } public void Reset() => _index = -1; } /// (T value, int index) public static IndexedEnumerable Enumerate(this T[] arr, int startIndex = 0) => new IndexedEnumerable(arr, startIndex); } public static class IEnumerableExtensions { public static IEnumerable Log(this IEnumerable source) { Console.WriteLine(string.Join(' ', source)); return source; } public static ScanEnumerable Scan( this IEnumerable source, TAccumulate seed, Func accumulator) where TSource : struct where TAccumulate : struct { return new ScanEnumerable(source, accumulator, seed); } public static IEnumerable ScanExSeed( this IEnumerable source, TAccumulate seed, Func accumulator) { var accumulation = new List(); var current = seed; foreach (var item in source) { current = accumulator(current, item); accumulation.Add(current); } return accumulation; } public readonly struct ScanEnumerable : IEnumerable where TSource : struct where TAccumulate : struct { private readonly IEnumerable _source; private readonly Func _accumulator; private readonly TAccumulate _seed; public ScanEnumerable(IEnumerable source, Func accumulator, TAccumulate seed) { _source = source; _accumulator = accumulator; _seed = seed; } public readonly ScanEnumerator GetEnumerator() => new(_source, _accumulator, _seed); readonly IEnumerator IEnumerable.GetEnumerator() => GetEnumerator(); readonly IEnumerator IEnumerable.GetEnumerator() => GetEnumerator(); } public struct ScanEnumerator : IEnumerator where TSource : struct where TAccumulate : struct { private readonly Func _accumulator; private readonly IEnumerator _enumerator; private TAccumulate _current; private bool _secondOrLaterElement = false; public ScanEnumerator(IEnumerable source, Func accumulator, TAccumulate seed) { _enumerator = source.GetEnumerator(); _accumulator = accumulator; _current = seed; } public readonly TAccumulate Current => _current; readonly object IEnumerator.Current => Current; public readonly void Dispose() { } public bool MoveNext() { if (_secondOrLaterElement) { if (_enumerator.MoveNext()) { _current = _accumulator(_current, _enumerator.Current); return true; } return false; } else { _secondOrLaterElement = true; return true; } } public void Reset() { throw new NotSupportedException(); } } public static IEnumerable Scan( this IEnumerable source, Func accumulator) { if (source is null) throw new ArgumentNullException(paramName: nameof(source)); if (accumulator is null) throw new ArgumentNullException(paramName: nameof(accumulator)); var accumulation = new List(); if (source.Any() is false) { return accumulation; } var current = source.First(); accumulation.Add(current); foreach (var item in source.Skip(1)) { current = accumulator(current, item); accumulation.Add(current); } return accumulation; } public static CombinationEnumerable Combination(this T[] a, int k) where T : IComparable => new(a, k); public readonly struct CombinationEnumerable where T : IComparable { private readonly T[] _a; private readonly int _k; public CombinationEnumerable(T[] a, int k) { _a = a; _k = k; } public readonly CombinationEnumerator GetEnumerator() => new(_a, _k); } public struct CombinationEnumerator : IEnumerator> where T : IComparable { private readonly int _k; private readonly T[] _a; private readonly int _n; private bool _secondOrLaterElement = false; public CombinationEnumerator(T[] a, int k) { _a = a; _n = a.Length; _k = k; } public readonly ReadOnlyMemory Current => _a.AsMemory()[.._k]; readonly object IEnumerator.Current => Current; public readonly void Dispose() { } public bool MoveNext() { if (_secondOrLaterElement) { return CombinationFunction.NextCombination(_a, 0, _k, _n); } else { _secondOrLaterElement = true; return true; } } public void Reset() { throw new NotSupportedException(); } } public static PermutationEnumerable Permutation(this T[] a) where T : IComparable => new(a); public static PermutationEnumerable Permutation(this Span a) where T : IComparable => new(a); public readonly ref struct PermutationEnumerable where T : IComparable { private readonly Span _a; public PermutationEnumerable(T[] a) => _a = a; public PermutationEnumerable(Span a) => _a = a; public readonly PermutationEnumerator GetEnumerator() => new(_a); } public ref struct PermutationEnumerator where T : IComparable { private readonly Span _a; private readonly int _n; private bool _secondOrLaterElement = false; public PermutationEnumerator(T[] a) { _a = a; _n = a.Length; } public PermutationEnumerator(Span a) { _a = a; _n = a.Length; } public readonly ReadOnlyMemory Current => _a.ToArray().AsMemory()[..]; public readonly void Dispose() { } public bool MoveNext() { if (_secondOrLaterElement) { return PermutationFunction.NextPermutation(_a); } else { _secondOrLaterElement = true; return true; } } public void Reset() => throw new NotSupportedException(); } } public class MyMath { public static long Pow(long x, int y) => Enumerable.Repeat(x, y).Aggregate(1L, (acc, x) => acc * x); public static long Pow10(int y) => Pow(10, y); public static long Pow2(int y) => Pow(2, y); public static long Gcd(long a, long b) => b == 0 ? a : Gcd(b, a % b); public static long Lcm(long a, long b) => a / Gcd(a, b) * b; } public class MyMathBigInteger { public static BigInteger Pow(long x, int y) => Enumerable.Repeat(x, y).Aggregate(new BigInteger(1), (acc, x) => acc * x); public static BigInteger Pow10(int y) => Pow(10, y); public static BigInteger Pow2(int y) => Pow(2, y); } } #region Expanded by https://github.com/kzrnm/SourceExpander namespace SourceExpander{public class Expander{[Conditional("EXP")]public static void Expand(string inputFilePath=null,string outputFilePath=null,bool ignoreAnyError=true){}public static string ExpandString(string inputFilePath=null,bool ignoreAnyError=true){return "";}}} #endregion Expanded by https://github.com/kzrnm/SourceExpander