Problem:
Score : 600 points

Problem Statement

We have N colored balls arranged in a row from left to right; the color of the i-th ball from the left is c_i.

You are given Q queries. The i-th query is as follows: how many different colors do the l_i-th through r_i-th balls from the left have?

Constraints

1\leq N,Q \leq 5 \times 10^5

1\leq c_i \leq N

1\leq l_i \leq r_i \leq N

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N Q
c_1 c_2 \cdots c_N
l_1 r_1
l_2 r_2
:
l_Q r_Q

Output

Print Q lines. The i-th line should contain the response to the i-th query.

Sample Input 1

4 3
1 2 1 3
1 3
2 4
3 3

Sample Output 1

2
3
1

The 1-st, 2-nd, and 3-rd balls from the left have the colors 1, 2, and 1 - two different colors.

The 2-st, 3-rd, and 4-th balls from the left have the colors 2, 1, and 3 - three different colors.

The 3-rd ball from the left has the color 1 - just one color.

Sample Input 2

10 10
2 5 6 5 2 1 7 9 7 2
5 5
2 4
6 7
2 2
7 8
7 9
1 8
6 9
8 10
6 8

Sample Output 2

1
2
2
1
2
2
6
3
3
3

Solution in C# (.NET Core 3.1.201) (judge verdict: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Text;
using System.Diagnostics;
using System.Numerics;
using static System.Console;
using static System.Convert;
using static System.Math;
using static Template;

class Solver
{
    public Scanner sc;
    public void Solve()
    {
        int N, Q;
        sc.Make(out N, out Q);
        var s = Create(N, () => new List<int>());
        var C = sc.ArrInt;
        var last = Create(N, () => -1);
        for(int i = 0; i < N; i++)
        {
            --C[i];
            if (last[C[i]] != -1) { s[last[C[i]]].Add(i); }
            last[C[i]] = i;
        }
        var seg = new SegmentTreeFractionalCascading(s);
        while (Q-- > 0)
        {
            int l, r;
            sc.ArrInt.Out(out l, out r);l--;
            Console.WriteLine(r - l - seg.Query(l, r, l, r));
        }
    }
}

class SegmentTreeFractionalCascading
{
    int[][] seg;
    int[][] L, R;
    int sz;
    public SegmentTreeFractionalCascading(List<int>[] A)
    {
        sz = 1;
        while (sz < A.Length) sz <<= 1;
        seg = new int[2 * sz - 1][];
        L = new int[2 * sz - 1][];
        R = new int[2 * sz - 1][];
        for (int i = 0; i < sz; i++)
        {
            if (i < A.Length)
            {
                seg[i + sz - 1] = A[i].ToArray();
                Array.Sort(seg[i + sz - 1], (a, b) => a - b);
            }
            else
            {
                seg[i + sz - 1] = new int[0];
            }
        }
        for (int k = sz - 2; k >= 0; k--)
        {
            seg[k] = new int[seg[2 * k + 1].Length + seg[2 * k + 2].Length];
            L[k] = new int[seg[k].Length + 1];
            R[k] = new int[seg[k].Length + 1];
            int t1 = 0, t2 = 0;
            for (int i = 0; i < seg[k].Length; i++)
            {
                L[k][i] = t1;
                R[k][i] = t2;
                if (t1 == seg[2 * k + 1].Length)
                {
                    seg[k][i] = seg[2 * k + 2][t2++];
                }
                else if (t2 == seg[2 * k + 2].Length)
                {
                    seg[k][i] = seg[2 * k + 1][t1++];
                }
                else
                {
                    if (seg[2 * k + 1][t1] < seg[2 * k + 2][t2])
                        seg[k][i] = seg[2 * k + 1][t1++];
                    else
                        seg[k][i] = seg[2 * k + 2][t2++];
                }
            }
            L[k][seg[k].Length] = seg[2 * k + 1].Length;
            R[k][seg[k].Length] = seg[2 * k + 2].Length;
        }
    }
    public long Query(int l, int r, int d, int u)
    {
        d = LowerBound(seg[0], d);
        u = LowerBound(seg[0], u);
        return Query(l, r, d, u, 0, 0, sz);
    }
    long Query(int l, int r, int lw, int up, int k, int lft, int rgt)
    {
        if (rgt <= l || r <= lft) return 0;
        if (l <= lft && rgt <= r) return up - lw;
        return Query(l, r, L[k][lw], L[k][up], 2 * k + 1, lft, (lft + rgt) >> 1) + Query(l, r, R[k][lw], R[k][up], 2 * k + 2, (lft + rgt) >> 1, rgt);
    }
    #region UpperBound/LowerBound
    public static int UpperBound<T>(IList<T> array, T value, Comparison<T> cmp = null)
    {
        cmp = cmp ?? Comparer<T>.Default.Compare;
        var low = -1;
        var high = array.Count;
        while (high - low > 1)
        {
            var mid = (high + low) / 2;
            if (cmp(array[mid], value) == 1) high = mid;
            else low = mid;
        }
        return high;
    }

    public static int LowerBound<T>(IList<T> array, T value, Comparison<T> cmp = null)
    {
        cmp = cmp ?? Comparer<T>.Default.Compare;
        var low = -1;
        var high = array.Count;
        while (high - low > 1)
        {
            var mid = (high + low) / 2;
            if (cmp(array[mid], value) != -1) high = mid;
            else low = mid;
        }
        return high;
    }
    #endregion
}
#region Template
public static class Template
{
    static void Main(string[] args)
    {
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        var sol = new Solver() { sc = new Scanner() };
        //var th = new Thread(sol.Solve, 1 << 26);th.Start();th.Join();
        sol.Solve();
        Console.Out.Flush();
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmin<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) > 0) { a = b; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool chmax<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(ref T a, ref T b) { var t = b; b = a; a = t; }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void swap<T>(this IList<T> A, int i, int j) { var t = A[i]; A[i] = A[j]; A[j] = t; }
    public static T[] Create<T>(int n, Func<T> f) { var rt = new T[n]; for (var i = 0; i < rt.Length; ++i) rt[i] = f(); return rt; }
    public static T[] Create<T>(int n, Func<int, T> f) { var rt = new T[n]; for (var i = 0; i < rt.Length; ++i) rt[i] = f(i); return rt; }
    public static void Out<T>(this IList<T> A, out T a) => a = A[0];
    public static void Out<T>(this IList<T> A, out T a, out T b) { a = A[0]; b = A[1]; }
    public static void Out<T>(this IList<T> A, out T a, out T b, out T c) { A.Out(out a, out b); c = A[2]; }
    public static void Out<T>(this IList<T> A, out T a, out T b, out T c, out T d) { A.Out(out a, out b, out c); d = A[3]; }
    public static string Concat<T>(this IEnumerable<T> A, string sp) => string.Join(sp, A);
    public static char ToChar(this int s, char begin = '0') => (char)(s + begin);
    public static IEnumerable<T> Shuffle<T>(this IEnumerable<T> A) => A.OrderBy(v => Guid.NewGuid());
    public static int CompareTo<T>(this T[] A, T[] B, Comparison<T> cmp = null) { cmp = cmp ?? Comparer<T>.Default.Compare; for (var i = 0; i < Min(A.Length, B.Length); i++) { int c = cmp(A[i], B[i]); if (c > 0) return 1; else if (c < 0) return -1; } if (A.Length == B.Length) return 0; if (A.Length > B.Length) return 1; else return -1; }
    public static int ArgMax<T>(this IList<T> A, Comparison<T> cmp = null) { cmp = cmp ?? Comparer<T>.Default.Compare; T max = A[0]; int rt = 0; for (int i = 1; i < A.Count; i++) if (cmp(max, A[i]) < 0) { max = A[i]; rt = i; } return rt; }
    public static T PopBack<T>(this List<T> A) { var v = A[A.Count - 1]; A.RemoveAt(A.Count - 1); return v; }
    public static void Fail<T>(T s) { Console.WriteLine(s); Console.Out.Close(); Environment.Exit(0); }
}
public class Scanner
{
    public string Str => Console.ReadLine().Trim();
    public int Int => int.Parse(Str);
    public long Long => long.Parse(Str);
    public double Double => double.Parse(Str);
    public int[] ArrInt => Str.Split(' ').Select(int.Parse).ToArray();
    public long[] ArrLong => Str.Split(' ').Select(long.Parse).ToArray();
    public char[][] Grid(int n) => Create(n, () => Str.ToCharArray());
    public int[] ArrInt1D(int n) => Create(n, () => Int);
    public long[] ArrLong1D(int n) => Create(n, () => Long);
    public int[][] ArrInt2D(int n) => Create(n, () => ArrInt);
    public long[][] ArrLong2D(int n) => Create(n, () => ArrLong);
    private Queue<string> q = new Queue<string>();
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public T Next<T>() { if (q.Count == 0) foreach (var item in Str.Split(' ')) q.Enqueue(item); return (T)Convert.ChangeType(q.Dequeue(), typeof(T)); }
    public void Make<T1>(out T1 v1) => v1 = Next<T1>();
    public void Make<T1, T2>(out T1 v1, out T2 v2) { v1 = Next<T1>(); v2 = Next<T2>(); }
    public void Make<T1, T2, T3>(out T1 v1, out T2 v2, out T3 v3) { Make(out v1, out v2); v3 = Next<T3>(); }
    public void Make<T1, T2, T3, T4>(out T1 v1, out T2 v2, out T3 v3, out T4 v4) { Make(out v1, out v2, out v3); v4 = Next<T4>(); }
    public void Make<T1, T2, T3, T4, T5>(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<T5>(); }
    public void Make<T1, T2, T3, T4, T5, T6>(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<T6>(); }
    public void Make<T1, T2, T3, T4, T5, T6, T7>(out T1 v1, out T2 v2, out T3 v3, out T4 v4, out T5 v5, out T6 v6, out T7 v7) { Make(out v1, out v2, out v3, out v4, out v5, out v6); v7 = Next<T7>(); }
    public (T1, T2) Make<T1, T2>() { Make(out T1 v1, out T2 v2); return (v1, v2); }
    public (T1, T2, T3) Make<T1, T2, T3>() { Make(out T1 v1, out T2 v2, out T3 v3); return (v1, v2, v3); }
    public (T1, T2, T3, T4) Make<T1, T2, T3, T4>() { Make(out T1 v1, out T2 v2, out T3 v3, out T4 v4); return (v1, v2, v3, v4); }
}

#endregion