Remove Duplicates From Sorted List

Given a sorted linked list, remove the duplicates such that each element appears only once. The input will be a series of integers representing the linked list elements, separated by spaces. The last integer will be -1, which signifies the end of the list. Output the modified linked list in the same space-separated format, ending with -1. Example Input: 1 1 2 -1 Example Output: 1 2 -1