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++ (GCC 9.2.1) (judge verdict: Time Limit Exceeded)

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define endl "\n"
#define fast_io ios::sync_with_stdio(false);cin.tie(NULL);
#define input freopen("Test.txt","r",stdin)
#define output freopen("Output.txt","w",stdout);
#define what_is(x) cout<<#x<<" is "<<x<<endl;
#define pb push_back
#define eb emplace_back
#define inf 1000000000
const double pi = 3.141592653589793238460;

#define BLOCK 707  ///This is for dividing the array into blocks like we do in sqrt decomposition so as to sort them according to the block number
///this is the reason it takes O(sqrt(N)*N) time complexity

const int maxn = 500010;
struct query
{
	int l;
	int r;
	int i;
};
query Q[maxn];
int arr[maxn], ans[maxn];
int fre[1000001];
int cnt = 0;

bool comp(query a, query b)
{
	if (a.l / BLOCK != b.l / BLOCK)
		return a.l / BLOCK < b.l / BLOCK;
	return a.r < b.r;
}

void add(int pos)
{
	fre[arr[pos]]++;
	if (fre[arr[pos]] == 1)
		cnt++;
}
void remove(int pos)
{
	fre[arr[pos]]--;
	if (fre[arr[pos]] == 0)
		cnt--;

}
int main()
{
	fast_io;
	//input;
	//output;
	int n, q;
	cin >> n >> q;
	for (int i = 0; i < n; i++)
		cin >> arr[i];
	// cin >> q;
	for (int i = 0; i < q; i++)
	{
		cin >> Q[i].l >> Q[i].r;
		Q[i].i = i, Q[i].l--, Q[i].r--;
	}

	sort(Q, Q + q, comp);

	int ML = 0, MR = -1;
	for (int i = 0; i < q; i++)
	{
		int L = Q[i].l;
		int R = Q[i].r;

		while (ML > L)
			ML--, add(ML);
		while (MR < R)
			MR++, add(MR);
		while (ML < L)
			remove(ML), ML++;
		while (MR > R)
			remove(MR), MR--;
		ans[Q[i].i] = cnt;
	}

	for (int i = 0; i < q; i++)
		cout << ans[i] << endl;

	return 0;
}