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: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds;   
#define ordered_set tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> 
#define ld long double
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define all(a) a.begin(),a.end()
#define sz(a) (ll)(a.size())
const int M=5e5+5;
int bit[M],c[M],l[M],r[M],ans[M],ind[M];
stack<int> st[M];
bool cmp(int x,int y)
{
	return r[x]>r[y];
}
int query(int x)
{
	int ans=0;
	while(x)
	{
		ans+=bit[x];
		x-=(x&(-x));
	}
	return ans;
}
void update(int x,int z,int n)
{
	for(;x<=n;x+=(x&(-x)))
	{
		bit[x]+=z;
	}
}
int main()
{
	int n,q;
	cin>>n>>q;
	for(int i=1;i<=n;i++)
	{
		cin>>c[i];
		st[c[i]].push(i);
	}
	for(int i=1;i<=n;i++)
	{
		if(sz(st[i]))
		{
			int z = st[i].top();
			update(z,1,n);
		}
	}
	for(int i=1;i<=q;i++)
	{
		cin>>l[i]>>r[i];
		ind[i]=i;
	}
	sort(ind+1,ind+q+1,cmp);
	int j=1;
	for(int i=n;i>=1;i--)
	{
		while(j<=q && r[ind[j]]==i)
		{
			ans[ind[j]] = query(i)-query(l[ind[j]]-1);
			j++;
		}
		update(i,-1,n);
		st[c[i]].pop();
		if(sz(st[c[i]]))
		{
			int x = st[c[i]].top();
			update(x,1,n);
		}
	}
	for(int i=1;i<=q;i++)
		cout<<ans[i]<<"\n";
	return 0;
}