using System; using System.Collections; using System.Collections.Generic; using System.Diagnostics; using System.Globalization; using System.IO; using System.Text; using System.Linq; using E = System.Linq.Enumerable; using System.Threading; using System.Numerics; internal partial class Solver { public void Run() { var n = ni(); var a = ni(n); var ans1 = Solve(a); for (int i = 0; i < n; i++) { a[i] = -a[i]; } var ans2 = Solve(a); cout.WriteLine(Math.Max(ans1, ans2)); } private int Solve(int[] a) { var n = a.Length; var d = new IndexDictionary(a); var segR = new SegmentTree(Math.Max, int.MinValue); segR.Build(n + 1, i => 0); var dpR = new int[n]; for (int i = n - 1; i >= 0; i--) { var index = d.IndexOf(a[i]); dpR[i] = (segR.Query(index + 1, n + 1) + 1); segR[index] = dpR[i]; } var segL = new SegmentTree(Math.Max, int.MinValue); segL.Build(n + 1, i => 0); var dpL = new int[n]; for (int i = 0; i < n; i++) { var index = d.IndexOf(a[i]); dpL[i] = (segL.Query(index + 1, n + 1) + 1); segL[index] = dpL[i]; } int ans = 0; for (int i = 0; i < n; i++) { ans = Math.Max(ans, Math.Min(dpL[i], dpR[i]) - 1); } /*a.TextDump(); dpL.TextDump(); dpR.TextDump();*/ return ans; } } public sealed class SegmentTree { public int Count { get; private set; } private TMonoid[] _node; private readonly TMonoid _identity; private readonly Func _merge; public SegmentTree(Func merge, TMonoid identity) { _merge = merge; _identity = identity; } public void Build(IList array) { Build(array.Count, i => array[i]); } public void Build(int n, Func create) { Count = n; _node = new TMonoid[2 * Count]; for (int i = 0; i < n; i++) { _node[i + Count] = create(i); } for (int i = Count - 1; i > 0; i--) { _node[i] = _merge(_node[i << 1], _node[i << 1 | 1]); } } public void Set(int index, TMonoid val) { int p = index + Count; _node[p] = val; while (p > 0) { p >>= 1; _node[p] = _merge(_node[p << 1], _node[p << 1 | 1]); } } public TMonoid Query(int begin, int end) { TMonoid lv = _identity, rv = _identity; int l = begin + Count; int r = end + Count - 1; for (; l <= r; l >>= 1, r >>= 1) { if ((l & 1) == 1) { lv = _merge(lv, _node[l++]); } if ((r & 1) == 0) { rv = _merge(_node[r--], rv); } } return _merge(lv, rv); } public TMonoid this[int index] { get { return _node[index + Count]; } set { Set(index, value); } } }; public class IndexDictionary { private readonly Dictionary _toIndex; private readonly T[] _array; public IndexDictionary(IEnumerable source) : this(source, Comparer.Default.Compare) { } public IndexDictionary(IEnumerable source, Comparison comparison) { _array = source.Distinct().ToArray(); Array.Sort(_array, comparison); _toIndex = new Dictionary(_array.Length); int index = -1; foreach (var x in _array) { _toIndex[x] = ++index; } } public int Count { get { return _array.Length; } } public T this[int index] { get { return _array[index]; } } public int IndexOf(T value) { return _toIndex[value]; } public T[] ToArray() { return _array.ToArray(); } } // PREWRITEN CODE BEGINS FROM HERE static public class StringExtensions { static public string JoinToString(this IEnumerable source, string separator = " ") { return string.Join(separator, source); } } internal partial class Solver : Scanner { static readonly int? StackSizeInMebiByte = null; //50; public static void StartAndJoin(Action action, int maxStackSize) { var thread = new Thread(new ThreadStart(action), maxStackSize); thread.Start(); thread.Join(); } public static void Main() { #if LOCAL byte[] inputBuffer = new byte[1000000]; var inputStream = Console.OpenStandardInput(inputBuffer.Length); using (var reader = new StreamReader(inputStream, Console.InputEncoding, false, inputBuffer.Length)) { Console.SetIn(reader); new Solver(Console.In, Console.Out).Run(); } #else Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }); if (StackSizeInMebiByte.HasValue) { StartAndJoin(() => new Solver(Console.In, Console.Out).Run(), StackSizeInMebiByte.Value * 1024 * 1024); } else { new Solver(Console.In, Console.Out).Run(); } Console.Out.Flush(); #endif } #pragma warning disable IDE0052 private readonly TextReader cin; private readonly TextWriter cout; private readonly TextWriter cerr; #pragma warning restore IDE0052 public Solver(TextReader reader, TextWriter writer) : base(reader) { cin = reader; cout = writer; cerr = Console.Error; } public Solver(string input, TextWriter writer) : this(new StringReader(input), writer) { } #pragma warning disable IDE1006 #pragma warning disable IDE0051 private int ni() { return NextInt(); } private int[] ni(int n) { return NextIntArray(n); } private long nl() { return NextLong(); } private long[] nl(int n) { return NextLongArray(n); } private double nd() { return NextDouble(); } private double[] nd(int n) { return NextDoubleArray(n); } private string ns() { return Next(); } private string[] ns(int n) { return NextArray(n); } #pragma warning restore IDE1006 #pragma warning restore IDE0051 } #if DEBUG internal static class LinqPadExtension { public static string TextDump(this T obj) { if (obj is IEnumerable) return (obj as IEnumerable).Cast().JoinToString().Dump(); else return obj.ToString().Dump(); } public static T Dump(this T obj) { return LINQPad.Extensions.Dump(obj); } } #endif public class Scanner { private readonly TextReader Reader; private readonly CultureInfo ci = CultureInfo.InvariantCulture; private readonly char[] buffer = new char[2 * 1024]; private int cursor = 0, length = 0; private string Token; private readonly StringBuilder sb = new StringBuilder(1024); public Scanner() : this(Console.In) { } public Scanner(TextReader reader) { Reader = reader; } public int NextInt() { return checked((int)NextLong()); } public long NextLong() { var s = Next(); long r = 0; int i = 0; bool negative = false; if (s[i] == '-') { negative = true; i++; } for (; i < s.Length; i++) { r = r * 10 + (s[i] - '0'); #if DEBUG if (!char.IsDigit(s[i])) throw new FormatException(); #endif } return negative ? -r : r; } public double NextDouble() { return double.Parse(Next(), ci); } public string[] NextArray(int size) { string[] array = new string[size]; for (int i = 0; i < size; i++) { array[i] = Next(); } return array; } public int[] NextIntArray(int size) { int[] array = new int[size]; for (int i = 0; i < size; i++) { array[i] = NextInt(); } return array; } public long[] NextLongArray(int size) { long[] array = new long[size]; for (int i = 0; i < size; i++) { array[i] = NextLong(); } return array; } public double[] NextDoubleArray(int size) { double[] array = new double[size]; for (int i = 0; i < size; i++) { array[i] = NextDouble(); } return array; } public string Next() { if (Token == null) { if (!StockToken()) { throw new Exception(); } } var token = Token; Token = null; return token; } public bool HasNext() { if (Token != null) { return true; } return StockToken(); } private bool StockToken() { while (true) { sb.Clear(); while (true) { if (cursor >= length) { cursor = 0; if ((length = Reader.Read(buffer, 0, buffer.Length)) <= 0) { break; } } var c = buffer[cursor++]; if (33 <= c && c <= 126) { sb.Append(c); } else { if (sb.Length > 0) break; } } if (sb.Length > 0) { Token = sb.ToString(); return true; } return false; } } }