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;
int n,m;
const int Maxn=3e7;
int a[500005],li[500005];
struct t{
	int ls,rs,sum;
}tree[Maxn];
int root[500005];
int tot=0;
int build(int l,int r){
	int now=++tot;
	if(l==r)return now;
	int mid=(l+r)/2;
	tree[now].ls=build(l,mid);
	tree[now].rs=build(mid+1,r);
	return now;
}
int modify(int now,int l,int r,int goal,int sum){//
	int pos=++tot;
	tree[pos]=tree[now];
//	cout<<"l:"<<l<<" r:"<<r<<endl;
	if(l==r){
		tree[pos].sum+=sum;
		return pos;
	}
	int mid=(l+r)>>1;
	if(goal<=mid){
		tree[pos].ls=modify(tree[now].ls,l,mid,goal,sum);
	}
	else if(goal>mid){
		tree[pos].rs=modify(tree[now].rs,mid+1,r,goal,sum);
	}
	tree[pos].sum=tree[tree[pos].ls].sum+tree[tree[pos].rs].sum;
	
	return pos;
}
int anss=0;
void query(int pos1,int pos2,int l,int r){
//	cout<<"l:"<<l<<" r:"<<r<<endl;
	if(l==r){
//		cout<<tree[pos2].sum<<"\t"<<tree[pos1].sum<<endl; 
		if(tree[pos2].sum-tree[pos1].sum>0)anss++;
		return ; 
	}
	int mid=(l+r)>>1;
	query(tree[pos1].ls,tree[pos2].ls,l,mid);
	query(tree[pos1].rs,tree[pos2].rs,mid+1,r);
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		li[i]=a[i];
	}
	sort(li+1,li+1+n);
	int ed=unique(li+1,li+1+n)-li;
//	cout<<"alive"<<endl;
	root[0]=build(1,ed-1);
//	cout<<"alive"<<endl; 
	for(int i=1;i<=n;i++){
//		cout<<"alive"<<i<<endl;
		int sum=lower_bound(li+1,li+ed,a[i])-li;
		root[i]=modify(root[i-1],1,ed-1,sum,1);
//		cout<<"alive"<<i<<endl;
	}
	int l,r;
	for(int i=1;i<=m;i++){
		cin>>l>>r;
		anss=0;
		query(root[l-1],root[r],1,ed-1);
		cout<<anss<<endl;
	}
	return 0;
}