void insertFirst(book_list* b1, book* b) {
    book* tmp = b1->first;
    int ifExist = 0;
    do{
        if(strcmp(tmp->title,b->title)==0) {
            tmp->copies += b->copies;
            ifExist=1;
        }
    }while(tmp!=b1->first);

    if(ifExist==0) {
        b->next = b1->first;
        b1->first = b;
        b1->last->next = b1->first;
    }
}