Shared code

#include <algorithm>
#include <bits/stdc++.h>
#include <climits>
#include <deque>
#include <ext/pb_ds/assoc_container.hpp>
#include <iterator>
#include <numeric>
#include <vector>
using namespace std;
using namespace __gnu_pbds;

#ifndef LOCAL
#endif
#define all(x) (x).begin(), (x).end()
#define allr(x) (x).rbegin(), (x).rend()
typedef long long ll;
template <typename T, typename comp = less<T>>
using ordered_set =
  tree<T, null_type, comp, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T> using min_heap = priority_queue<T, vector<T>, greater<T>>;

template <typename T> class vect1 : public vector<T> {
public:
  using vector<T>::vector;
  T& operator[](size_t idx) {
    return this->at(idx - 1);
  }
};

#define int long long

int block_size;
struct query {
  int l, r, idx;
  friend bool operator<(query q1, query q2) {
    return make_pair(q1.l / block_size,
                     (q1.l / block_size & 1) ? q1.r : -q1.r) <
           make_pair(q2.l / block_size, (q2.l / block_size & 1) ? q2.r : -q2.r);
  }
};

vect1<int> ht;

int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n, q;
  cin >> n >> q;
  block_size = (int)sqrt((long double)n);
  vect1<int> arr(n);
  for (auto& a : arr)
    cin >> a;
  {
    int sz = 0;
    map<int, int> mp;
    for (auto& a : arr)
      mp[a];
    for (auto &[k, v] : mp)
      v = ++sz;
    for (auto& a : arr)
      a = mp[a];
    ht.resize(sz, 0);
  }
  ll cnt = 0;

  auto add = [&](int val) {
    if (ht[val] == 0)
      cnt++;
    ht[val]++;
  };

  auto remove = [&](int val) {
    ht[val]--;
    if (ht[val] == 0)
      cnt--;
  };

  vect1<int> ans(q);
  vect1<query> queries(q);

  for (int i = 1; i <= q; i++)
    cin >> queries[i].l >> queries[i].r, queries[i].idx = i;

  sort(all(queries));

  int cur_l = 1, cur_r = 0;

  for (auto &[ql, qr, idx] : queries) {

    while (cur_l > ql)
      add(arr[--cur_l]);

    while (cur_l < ql)
      remove(arr[cur_l++]);

    while (cur_r > qr)
      remove(arr[cur_r--]);

    while (cur_r < qr)
      add(arr[++cur_r]);

    ans[idx] = cnt;
  }

  for (auto& a : ans)
    cout << a << '\n';
}