When using a semaphore to ensure the child thread runs before the parent executes further as in the code snippet below, what value should the semaphore be initialized too (i.e., what should X be)?

sem_t s;
void *child(void *arg) {
  printf("child");
  sem_post(&s); // signal here: child is done
  return NULL;
}
   
int main(int argc, char *argv[]) {
  sem_init(&s, 0, X); // what should X be?
  printf("parent: begin");
  pthread_t c;
  pthread_create(c, NULL, child, NULL);
  sem_wait(&s); // wait here for child
  printf("parent: end");
  return 0;
}