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 static System.Math;
using static System.Console;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System;

namespace AtCoder
{
    class Program
    {
        private static long mod = 1000000007;
        static void Main(string[] args)
        {
            //var k = int.Parse(ReadLine());
            var line = ReadLine().Split(' ').Select(value => long.Parse(value)).ToArray();

            var n = line[0];
            var q = line[1];

            var cArray = ReadLine().Split(' ').Select(value => int.Parse(value)).ToArray();
            var size = (int)Floor(Sqrt(n));
            var hashSetNum = n / size;
            if(n % size != 0)
            {
                hashSetNum++;
            }
            var hashSetList = new List<HashSet<int>>();
            for(var i = 0; i < hashSetNum; i++)
            {
                hashSetList.Add(new HashSet<int>());
            }
            for(var i = 0; i < n; i++)
            {
                hashSetList[i / size].Add(cArray[i]);
            }

            var answers = new List<int>();
            for(var i = 0; i < q; i++)
            {
                var query = ReadLine().Split(' ').Select(value => int.Parse(value) - 1).ToArray();
                var startHashSetNum = query[0] / size;
                var endHashSetNum = query[1] / size;

                var hashSet = new HashSet<int>();
                for(var j = startHashSetNum + 1; j < endHashSetNum; j++)
                {
                    foreach(var color in hashSetList[j])
                    {
                        hashSet.Add(color);
                    }
                }
                if(startHashSetNum == endHashSetNum)
                {
                    for(var j = query[0]; j <= query[1]; j++)
                    {
                        hashSet.Add(cArray[j]);
                    }
                }
                else
                {
                    for(var j = query[0]; j < (startHashSetNum + 1) * size; j++)
                    {
                        hashSet.Add(cArray[j]);
                    }
                    for(var j = endHashSetNum * size; j <= query[1]; j++)
                    {
                        hashSet.Add(cArray[j]);
                    }
                }

                answers.Add(hashSet.Count);
            }

            answers.ForEach(value => WriteLine(value));
        }
    }
}