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 Java (OpenJDK 11.0.6) (judge verdict: Time Limit Exceeded)

import java.util.*;

public class Main {


    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int q = sc.nextInt();
        int[] col = new int[n+1];
        for(int i=1; i<=n; i++) {
            col[i] = Integer.parseInt(sc.next());
        }

        int[] last = new int[n + 1];
        BIT bit = new BIT(n);

        int[] res = new int[q];
        List<Pair> list = new ArrayList<>();
        for(int i=0; i<q; i++) {
            list.add(new Pair(sc.nextInt(), sc.nextInt(), i));
        }
        list.sort((a, b) -> Integer.compare(a.r, b.r));

        int pos = 0;
        int sum = 0;
        for(Pair p : list) {
            while(pos < p.r) {
                int c = col[pos+1];
                if(last[c] >= 1) {
                    bit.add(last[c], -1);
                    sum--;
                }
                bit.add(pos+1, 1);
                sum++;
                last[c] = pos+1;
                pos++;
            }
            res[p.i] = sum - bit.sum(p.l-1);
        }
        for(int i=0 ;i<q; i++) {
            System.out.println(res[i]);
        }


    }

    static class Pair {
        int l;
        int r;
        int i;
        Pair(int l, int r, int i) {
            this.l = l;
            this.r = r;
            this.i = i;
        }
    }

    static class BIT {
        int n ;
        int[] bit;

        BIT(int n) {
            this.n = n;
            bit = new int[n+1];
        }

        void add(int i, int num) {
            while(i <= n) {
                bit[i] += num;
                int lsb =  i & (-i);
                i += lsb;
            }
        }

        int sum(int i) {
            int sum = 0;
            while(i > 0) {
                sum += bit[i];
                int lsb =  i & (-i);
                i -= lsb;
            }
            return sum;
        }

        int sum(int l, int r) {
            return sum(r) - sum(l-1);
        }
    }


}