typedef struct {
    element_t data;
    struct NODE *prev;
    struct NODE *child;
    struct NODE *sibling;
} NODE;

NODE *push(NODE *top, element_t data) {
    NODE *tempNode = (NODE*)malloc(sizeof(NODE));

    tempNode->data = data;
    tempNode->prev = top;
    top->sibling = tempNode;

    return tempNode;
}