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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * 解説通りに実装したソースコード
 * 
 * https://atcoder.jp/contests/abc174/submissions/15644133 と https://atcoder.jp/contests/abc174/submissions/15644479
 * にも参考<br/>
 * java.util.Scanner が遅いため、java.io.BufferedReaderを使用
 */
public class Main {

	public static void main(String[] args) {
		try (InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr)) {
			String[] strings = br.readLine().split(" ");
			int n = Integer.parseInt(strings[0]), q = Integer.parseInt(strings[1]);
			String[] cs = br.readLine().split(" ", n);
			@SuppressWarnings("unchecked")
			List<Integer>[] queryIndexes = new List[n + 1], queryLefts = new List[n + 1];
			for (int i = 0; i < q; i++) {
				String[] s = br.readLine().split(" ");
				int l = Integer.parseInt(s[0]), r = Integer.parseInt(s[1]);
				if (null == queryIndexes[r]) {
					queryIndexes[r] = new ArrayList<>();
				}
				queryIndexes[r].add(i);
				if (null == queryLefts[r]) {
					queryLefts[r] = new ArrayList<>();
				}
				queryLefts[r].add(l);
			}
			BinaryIndexedTree bit = new BinaryIndexedTree(n + 1);
			int[] answers = new int[q], indexes = new int[n + 1];
			Arrays.fill(indexes, 0);
			for (int i = 0; i < n; i++) {
				int c = Integer.parseInt(cs[i]);
				if (indexes[c] > 0) {
					bit.add(indexes[c], -1);
				}
				bit.add(i + 1, 1);
				indexes[c] = i + 1;
				if (null != queryIndexes[i + 1]) {
					for (int j = 0; j < queryIndexes[i + 1].size(); j++) {
						answers[queryIndexes[i + 1].get(j)] = bit.sum(queryLefts[i + 1].get(j), i + 1);
					}
				}
			}
			Arrays.stream(answers).forEach(System.out::println);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

//	private static class Query implements Comparable<Query> {
//		int index;
//		int left;
//		int right;
//
//		Query(int index, int left, int right) {
//			super();
//			this.index = index;
//			this.left = left;
//			this.right = right;
//		}
//
//		@Override
//		public int compareTo(Query o) {
//			return this.right - o.right;
//		}
//	}

	private static class BinaryIndexedTree {
		int size;
		int[] data;

		BinaryIndexedTree(int size) {
			super();
			this.size = size;
			data = new int[size];
			Arrays.fill(data, 0);
		}

		void add(int index, int value) {
			for (int i = index; i < size; i += (i & -i)) {
				data[i] += value;
			}
		}

		int sum(int index) {
			int sum = 0;
			for (int i = index; i > 0; i -= (i & -i)) {
				sum += data[i];
			}
			return sum;
		}

		int sum(int from, int to) {
			return sum(to) - sum(from - 1);
		}
	}
}