Problem p02642 (C++)

Buggy submission (status: Time Limit Exceeded):
//                                               KEEP GRINDING
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    new_data_set;

#define fastio                                                                 \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL);

#define int long long
#define ld long double
#define MOD 1000000007
#define mod 998244353
#define precise(i) fixed << setprecision(10) << i
#define f(i, a, b) for (int i = a; i < b; ++i)

#define endl '\n'
#define debug cout << "\n========================================\n" << endl;
#define err1(a) cout << #a << " " << a << endl;
#define err2(a, b) cout << #a << " " << a << " " << #b << " " << b << endl;
#define err3(a, b, c)                                                          \
  cout << #a << " " << a << " " << #b << " " << b << " " << #c << " " << c     \
       << endl;
#define err4(a, b, c, d)                                                       \
  cout << #a << " " << a << " " << #b << " " << b << " " << #c << " " << c     \
       << " " << #d << " " << d << endl;

#define all(a) a.begin(), a.end()
#define show(a)                                                                \
  for (auto xyz : a)                                                           \
    cout << xyz << " ";                                                        \
  cout << endl;
#define mx(a) *max_element(a)
#define mn(a) *min_element(a)
#define LB                                                                     \
  lower_bound // THIS GIVES THE ITR TO THE ELEMENT IN RANGE [SI,EI) THAT IS >=
              // OUR VALUE
#define UB                                                                     \
  upper_bound // THIS GIVES THE ITR TO THE ELEMENT IN RANGE [SI,EI) THAT IS >
              // OUR VALUE

#define fr first
#define sc second

#define MAXN 200005
#define INF 9223372036854775807
signed main() {
  fastio int n, ans = 0;
  cin >> n;
  vector<int> a(n);
  f(i, 0, n) cin >> a[i];
  sort(all(a));
  vector<int> b(1000010, 0);
  f(i, 0, n - 1) {
    if (a[i] == a[i + 1])
      b[a[i]] = 1;
  }
  f(i, 0, n) {
    for (int j = 2 * a[i]; j < 1000001; j += a[i])
      b[j] = 1;
  }
  f(i, 0, n) {
    if (!b[a[i]])
      ans++;
  }
  cout << ans;
}

Fixed submission:
//                                               KEEP GRINDING
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    new_data_set;

#define fastio                                                                 \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL);

#define int long long
#define ld long double
#define MOD 1000000007
#define mod 998244353
#define precise(i) fixed << setprecision(10) << i
#define f(i, a, b) for (int i = a; i < b; ++i)

#define endl '\n'
#define debug cout << "\n========================================\n" << endl;
#define err1(a) cout << #a << " " << a << endl;
#define err2(a, b) cout << #a << " " << a << " " << #b << " " << b << endl;
#define err3(a, b, c)                                                          \
  cout << #a << " " << a << " " << #b << " " << b << " " << #c << " " << c     \
       << endl;
#define err4(a, b, c, d)                                                       \
  cout << #a << " " << a << " " << #b << " " << b << " " << #c << " " << c     \
       << " " << #d << " " << d << endl;

#define all(a) a.begin(), a.end()
#define show(a)                                                                \
  for (auto xyz : a)                                                           \
    cout << xyz << " ";                                                        \
  cout << endl;
#define mx(a) *max_element(a)
#define mn(a) *min_element(a)
#define LB                                                                     \
  lower_bound // THIS GIVES THE ITR TO THE ELEMENT IN RANGE [SI,EI) THAT IS >=
              // OUR VALUE
#define UB                                                                     \
  upper_bound // THIS GIVES THE ITR TO THE ELEMENT IN RANGE [SI,EI) THAT IS >
              // OUR VALUE

#define fr first
#define sc second

#define MAXN 200005
#define INF 9223372036854775807
signed main() {
  fastio int n, ans = 0;
  cin >> n;
  vector<int> a(n);
  f(i, 0, n) cin >> a[i];
  sort(all(a));
  vector<int> b(1000010, 0);
  f(i, 0, n - 1) {
    if (a[i] == a[i + 1])
      b[a[i]] = 1;
  }
  for (int j = 2 * a[0]; j < 1000001; j += a[0])
    b[j] = 1;
  f(i, 1, n) {
    if (a[i] != a[i - 1])
      for (int j = 2 * a[i]; j < 1000001; j += a[i])
        b[j] = 1;
  }
  f(i, 0, n) {
    if (!b[a[i]])
      ans++;
  }
  cout << ans;
}