stud *create(void) {
  stud *prev, *current, *head;
  char check;
  head = prev = new stud;

  std::cout << "Введите фамилию: " << std::endl;
  std::cin >> prev->last_name;

  do {
    current = new stud;
    std::cout << "Введите фамилию: " << std::endl;
    std::cin >> current->last_name;
    prev->next = current;
    prev = current;
    std::cout << "Добавить еще одного студента? y/n " << std::endl;
    std::cin >> check;
    if (check == 'n')
      break;
  } while (1);

  current->next = NULL;
  return head;
}

void show(stud *head) {
  stud *current;
  current = head;
  while (current != NULL) {
    std::cout << current->last_name << ": ";
    for (int i = 0; i < 4; i++)
      std::cout << current->grades[i] << " ";
    std::cout << std::endl;
    current = current->next;
  }
}