SinglyLinkedListNode* removeDuplicates(SinglyLinkedListNode* llist) {
    SinglyLinkedListNode *current = llist, *prev = NULL ;
    
    while(current->next != 0){
        prev = current;
        current = current->next;
        if(prev->data == current->data){
            prev->next = current->next;
            current = prev;
        }
    }
    
    return llist;
}