struct data
    {
      int d;
      struct data *next;
    };
    typedef struct data Node;

    void insertCopy(int x, int n, Node **lis)
    {
      int pos = 1;

      Node *p, *head;

      head = *lis;

      if (lis == NULL)
      {
         p = NULL;
      }
      else
      {
        //first node
        if ((head->d == x) && (pos % n == 0))
        {
            p = newnode();
            p->d = x;
            p->next = head;
            *lis = p;
        }
      }

     if (head->next != NULL)
     {
        pos = 2;

        while(head->next != NULL)
        {
            if ((head->next->d == x) && (pos % n == 0))
            {
                p = newnode();
                p->d = x;
                p->next = head->next;
                head->next = p;
            }
            else
            {
                head = head->next;
            }
            pos++;
        }
     }
   }