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++ (Clang 10.0.0) (judge verdict: Runtime Error)

#include<iostream>
#include<vector>
#include<algorithm>
#include<set>
#include<cmath>
#include<iomanip>
using namespace std;
#define pb push_back
#define ll long long int
# define pll pair<ll,ll>
# define fio ios_base::sync_with_stdio(false); cin.tie(NULL)
# define ft first
# define sec second
int a[500009];
set<int>tree[500009];
set<int> merge(set<int> v1 , set<int> v2)
{
    set<int>S;
    S=v1;
    for(auto x : v2) S.insert(x);
    return S;
}
void build(int l , int r , int v)
{
    if(l<r)
    {
        int mid=(l+r)/2;
        build(l,mid,2*v);
        build(mid+1,r,2*v+1);
        tree[v]=merge(tree[2*v],tree[2*v+1]);
    }
    else tree[v]={a[l]};
}

set<int> query(int l , int r , int tl , int tr , int v)
{   if(l>r) return {};
    if(l==tl and r==tr) return tree[v];
    int mid=(tl+tr)/2;
    return merge( query(l,min(mid,r),tl,mid,2*v)  , query(max(l,mid+1),r,mid+1,tr,2*v+1) ) ;
}
int main()
{
    int n,q;
    cin>>n>>q;
    for(int i=1;i<=n;i++) cin>>a[i];
    build(1,n,1);
    int l ,r ;
    
    while(q--)
    {
        cin >> l>> r;
        cout << query(l,r,1,n,1).size() <<"\n";
    }
    
}