#include <stdio.h>
#include <stdlib.h>

typedef struct link {
  int data;
  struct link *next;
} * Link;

Link AppendNode(Link head, int data);
void DisplyNode(Link head);

int main() {
  int data;
  Link head = NULL;
  while (1) {
    scanf("%d", &data);
    if (data == -1)
      break;
    head = AppendNode(head, data);
  }
  if (head != NULL)
    DisplyNode(head);
  else
    printf("NULL");

  return 0;
}

/*在此实现 AppendNode函数 */
Link AppendNode(Link head, int data) {

  if (head == NULL) {
    head = malloc(sizeof(Link));
    head->next = NULL;
    head->data = data;
  } else {
    Link ptr = head;
    while (ptr->next != NULL) {
      ptr = ptr->next;
    }

    Link next = malloc(sizeof(Link));
    ptr->next = next;
    next->next = NULL;
    next->data = data;
  }

  return head;
}

/*在此实现DisplyNode函数 */
void DisplyNode(Link head) {
  printf("%d", head->data);
  Link ptr = head->next;

  while (ptr != NULL) {
    printf(",%d", ptr->data);
    ptr = ptr->next;
  }
}