Item *search(HashTable ht, Key k)
{
    int i = hash(k, ht->N);
    return ht->items[i];
}
void insert(HashTable ht, Item it)
{
    int i = hash(key(it), ht->N);
    ht->items[i] = newItem(it);
}
void delete(HashTable ht, Key k)
{
    int i = hash(k, ht->N);
    free(ht->items[i]);
    ht->items[i] = NULL;
}