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: Accepted)

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int q = Integer.parseInt(sa[1]);
		sa = br.readLine().split(" ");
		int[] c = new int[n];
		for (int i = 0; i < n; i++) {
			c[i] = Integer.parseInt(sa[i]);
		}
		Obj[] arr = new Obj[q];
		Obj[] arr2 = new Obj[q];
		for (int i = 0; i < q; i++) {
			sa = br.readLine().split(" ");
			Obj o = new Obj();
			o.i = i;
			o.l = Integer.parseInt(sa[0]);
			o.r = Integer.parseInt(sa[1]);
			arr[i] = o;
			arr2[i] = o;
		}
		br.close();

		int[] pre = new int[n + 1];
		Map<Integer, Integer> map = new HashMap<>();
		for (int i = 0; i < n; i++) {
			if (map.containsKey(c[i])) {
				pre[i + 1] = map.get(c[i]);
			}
			map.put(c[i], i + 1);
		}

		Arrays.sort(arr, (o1, o2) -> o1.r - o2.r);
		BIT bit = new BIT(n);
		int j = 1;
		for (Obj o : arr) {
			while (j <= o.r) {
				bit.add(j, 1);
				if (pre[j] > 0) {
					bit.add(pre[j], -1);
				}
				j++;
			}
			o.ans = bit.sum(o.r) - bit.sum(o.l - 1);
		}

		PrintWriter pw = new PrintWriter(System.out);
		for (int i = 0; i < q; i++) {
			pw.println(arr2[i].ans);
		}
		pw.flush();
	}

	static class Obj {
		int i, l, r;
		long ans;
	}

	static class BIT {
		int n;
		long[] arr;

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

		void add(int idx, long val) {
			for (int i = idx; i <= n; i += i & -i) {
				arr[i] += val;
			}
		}

		long sum(int idx) {
			long sum = 0;
			for (int i = idx; i > 0; i -= i & -i) {
				sum += arr[i];
			}
			return sum;
		}
	}
}