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: Wrong Answer)

/*** 𝕒𝕜𝕤𝕙𝕒𝕪𝕜𝕦𝕞𝕒𝕣𝟡𝟡 ***/

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
 
using namespace std;
using namespace __gnu_pbds;
 
template<typename T> using id_set = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update> ;
 
#define f(i,x,n) for(i=x;i<n;i++)
#define fr(i,x,n) for(i=x;i>=n;i--)
#define pu push_back           
#define pp pop_back
#define F first
#define S second
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define SP(x) fixed<<setprecision(x)
#define IOS() ios::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
 
const long long MOD=1e9+7;
const long double PI = acos(-1);
const long long INF=INT_MAX;
const long long LINF=LLONG_MAX;
const long long N=5e5+1;
 
typedef long long ll;
typedef long double ld;

ll blocksize=256, n, m, ans = 0;
vector<ll> a(N);
map<ll,ll> cont;

void remove(ll ind)
{
	if(cont[a[ind]] == 1)
		ans--;
    cont[a[ind]]--;
}
void add(ll ind)
{
    cont[a[ind]]++;
    if(cont[a[ind]] == 1)
		ans++;
}
ll getanswer()
{
    return ans;
}
struct Query
{
    ll l, r, ind;
    bool operator<(Query other) const
    {
        return make_pair(l/blocksize, r)<make_pair(other.l/blocksize, other.r);
    }
};

vector<ll> mosalgo(vector<Query> queries)
{
    vector<ll> answer(queries.size());
    sort(all(queries));
    ll curl=0, curr=-1;
    for(Query q : queries)
    {
        while(curl>q.l)
        {
            curl--;
            add(curl);
        }
        while(curr<q.r)
        {
            curr++;
            add(curr);
        }
        while(curl<q.l)
        {
            remove(curl);
            curl++;
        }
        while(curr>q.r)
        {
            remove(curr);
            curr--;
        }
        answer[q.ind]=getanswer();
    }
    return answer;
}

void test_case()
{
    ll i,j;
    cin>>n>>m;
    f(i,0,n)
    {
        cin>>a[i];
    }
    vector<Query> v;
    f(i,0,m)
    {
        ll x,y;
        cin>>x>>y;
        x--;
        v.pu({x,y,i});
    }
    vector<ll> res=mosalgo(v);
    f(i,0,m)
        cout<<res[i]<<'\n';

}

int main()
{
    IOS();
   
    int tc=1;
    // cin>>tc;
    while(tc--)
        test_case();
    return 0;
}