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>
#define ll long long
#define pb push_back
using namespace std;
const int nax=5e5+1;
vector<int> cnt(nax);
int blk=707;
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
   int n,q;
   cin>>n>>q;
   vector<int> a(n);
   for(int i=0;i<n;i++) cin>>a[i];
   vector<pair<pair<int,int>,int>> vec(q);
   for(int i=0;i<q;i++)
   {
       cin>> vec[i].first.first>>vec[i].first.second;
       vec[i].first.first--;
       vec[i].first.second--;
       vec[i].second=i;

   }
   
   sort(vec.begin(),vec.end(),[&](pair<pair<int,int>,int> x,pair<pair<int,int>,int> y){
      
       if((x.first.first/blk)!=(y.first.first/blk)) return (x.first.first/blk)<(y.first.first/blk);
       else return x.first.second<y.first.second;
       
   });
   int l=0,r=-1;
   vector<int> an(q);
   int ans=0;
   auto add=[&](int id){
       cnt[a[id]]++;
       if(cnt[a[id]]==1) ans++;
   };

   auto sub=[&](int id){
       cnt[a[id]]--;
       if(cnt[a[id]]==0) ans--;
   };

   for(int i=0;i<q;i++)
   {
       while(r<vec[i].first.second)
       {
           r++;
           add(r);
       }
        while(l<vec[i].first.first)
       {
           
           sub(l);
           l++;

       }
       while(r>vec[i].first.second)
       {
           sub(r);
           r--;
       }
      
       while(l>vec[i].first.first)
       {
           l--;
           add(l);
           

       }
      //if(l==r) ans--;
      an[vec[i].second]=ans;
       //cout<<ans<<endl;

   }
   for(auto it : an) cout<<it<<"\n";
}