#include <stdbool.h>
#include <stdlib.h>

typedef struct list_node_s {
  int value;
  struct list_node_s *next;
} list_node_t;


list_node_t *subtraction(list_node_t *head1, list_node_t *head2) {
  list_node_t *new_head, *new_ptr, *new_current;

  for (list_node_t *ptr1 = head1; ptr1 != NULL; ptr1 = ptr1->next) {
    bool found = false;

    for (list_node_t *ptr2 = head1; ptr2 != NULL; ptr2 = ptr2->next) {
      if (ptr1->value == ptr2->value) {
        found = true;
      }
    }

    if (found == false) {
      list_node_t *new_ptr = malloc(sizeof(list_node_t));

      new_ptr->value = ptr1->value;
      new_ptr->next = NULL;

      if (new_head == NULL) {
        new_head = new_ptr;
        new_current = new_ptr;
      } else {
        new_current->next = new_ptr;
        new_current = new_current;
      }
    }
  }

  return new_head;
}