typedef struct node {
    char *first;
    char *last;
    long number;
    struct node *nextFirst;
    struct node *nextLast;
} Node;

typedef struct mlist {
    Node *headFirstName;
    Node *headLastName;
} MultiLinkedList;

MultiLinkedList *add(MultiLinkedList *list, char *first, char *last, long num) {
    // allocate a new node
    Node *newNode = malloc ( sizeof(Node) );
    newNode->first = malloc ( strlen(first) + 1 );
    strcpy(newNode->first, first);
    newNode->last = malloc ( strlen(last) + 1 );
    strcpy(newNode->last, last);
    newNode->number = num;
    // add this new node at the head of the "byFirst" list
    newNode->nextFirst = list->headFirstName;
    list->headFirstName = newNode;
    // add this new node at the head of the "byLast" list
    newNode->nextLast = list->headLastName;
    list->headLastName = newNode;
    // return the multi-list object with updated head pointers
    return list;
}