#include <stdio.h>

typedef struct ListNode_ {
  int                 data;
  struct ListNode_*   next;

} ListNode, *Node;


ListNode newNode(){
  Node newOne = (Node)(malloc(sizeof(ListNode)));
  return newOne;
}

int main() {

  ListNode a, b;
  a = newNode();
  b = newNode();

  a->data = 3;
  b->data = 5;

  a->next = b;
  b->next = a;

  a->next->data = 17;    // change b's data.


}