using System; using System.Collections.Generic; using System.Linq; using System.IO; using System.Runtime.CompilerServices; using System.Text; using static Template; using static System.Console; using static System.Convert; using static System.Math; using Pi = Pair; using Number = System.Int64; class Solver { public void Solve() { var num = Input.num; var ar = Input.ar; var l = RLEncoding(ar); var dp = new int[l.Count+1]; dp[1] = l[0].v2; for(var i=2;i<=l.Count;i++) { dp[i] = Max(dp[i - 1], dp[i - 2] + l[i - 1].v2); } WriteLine(dp[l.Count]); } public static List> RLEncoding(IList list) where T : IEquatable { var ret = new List> { new Pair(list[0], 1) }; for (var i = 1; i < list.Count; i++) if (ret.Last().v1.Equals(list[i])) ret[ret.Count - 1].v2++; else ret.Add(new Pair(list[i], 1)); return ret; } } #region Template public class Template { [MethodImpl(MethodImplOptions.AggressiveInlining)] public static bool chmin(ref T num, T val) where T : IComparable { if (num.CompareTo(val) == 1) { num = val; return true; } return false; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static bool chmax(ref T num, T val) where T : IComparable { if (num.CompareTo(val) == -1) { num = val; return true; } return false; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void swap(ref T v1, ref T v2) { var t = v2; v2 = v1; v1 = t; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static T[] Create(int n, Func f) => Enumerable.Repeat(0, n).Select(_ => f()).ToArray(); public static void Fail() => Fail("No"); public static void Fail(T s) { Console.WriteLine(s); Console.Out.Close(); Environment.Exit(0); } static void Main(string[] args) { var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }; Console.SetOut(sw); var p = new Solver(); for (var i = 1; i > 0; --i) p.Solve(); Console.Out.Flush(); } } public class Input { public static string read => Console.ReadLine().Trim(); public static int[] ar => read.Split(' ').Select(int.Parse).ToArray(); public static int num => Convert.ToInt32(read); public static long[] arL => read.Split(' ').Select(long.Parse).ToArray(); public static long numL => Convert.ToInt64(read); public static char[][] grid(int h) => Create(h, () => read.ToCharArray()); public static int[] ar1D(int n) => Create(n, () => num); public static long[] arL1D(int n) => Create(n, () => numL); public static string[] strs(int n) => Create(n, () => read); public static int[][] ar2D(int n) => Create(n, () => ar); public static long[][] arL2D(int n) => Create(n, () => arL); public static List[] edge(int n) => Create(n, () => new List()); public static void Make(out T1 v1, out T2 v2) { v1 = Next(); v2 = Next(); } public static void Make(out T1 v1, out T2 v2, out T3 v3) { Make(out v1, out v2); v3 = Next(); } public static void Make(out T1 v1, out T2 v2, out T3 v3, out T4 v4) { Make(out v1, out v2, out v3); v4 = Next(); } public static void Make(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(); } public static void Make(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(); } static Input() { sc = new Queue(); dic = new Dictionary>(); dic[typeof(int)] = s => int.Parse(s); dic[typeof(long)] = s => long.Parse(s); dic[typeof(char)] = s => char.Parse(s); dic[typeof(double)] = s => double.Parse(s); dic[typeof(uint)] = s => uint.Parse(s); dic[typeof(ulong)] = s => ulong.Parse(s); dic[typeof(string)] = s => s; } private static Dictionary> dic; private static Queue sc; [MethodImpl(MethodImplOptions.AggressiveInlining)] public static T Next() { if (sc.Count == 0) foreach (var item in read.Split(' ')) sc.Enqueue(item); return (T)dic[typeof(T)](sc.Dequeue()); } public const int MOD = 1000000007; } public class Pair : IComparable> { public T1 v1; public T2 v2; public Pair() { v1 = default(T1);v2 = default(T2); } public Pair(T1 v1, T2 v2) { this.v1 = v1; this.v2 = v2; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public int CompareTo(Pair p) { var c = Comparer.Default.Compare(v1, p.v1); if (c == 0) c = Comparer.Default.Compare(v2, p.v2); return c; } public override string ToString() => $"{v1.ToString()} {v2.ToString()}"; } public class Pair : Pair, IComparable> { public T3 v3; public Pair() : base() { v3 = default(T3); } public Pair(T1 v1, T2 v2, T3 v3) : base(v1, v2) { this.v3 = v3; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public int CompareTo(Pair p) { var c = base.CompareTo(p); if (c == 0) c = Comparer.Default.Compare(v3, p.v3); return c; } public override string ToString() => $"{base.ToString()} {v3.ToString()}"; } #endregion