vector<int> euler_sieve(int n) {
  vector<bool> is_composite(n + 1, false);
  vector<int> primes;

  for (int i = 2; i <= n; i++) {
   if (!is_composite[i])
    primes.push_back(i);

   for (int j = 0; __________________________ && (long long)i * primes[j] <= n; j++) {
    is_composite[i * primes[j]] = true;

    if (i % primes[j] == 0)
     break;
   }
  }
  return primes;
}