<b_jonas> slashlearn aoc//Advent of Code (AoC) is a series of programming puzzles that some regulars enjoy, found at "https://adventofcode.com/2019/about".

#!/usr/bin/python
s=set()
try:
 while True:
  l=raw_input()
  if l not in s:
   s.add(l)
   print(l)
except EOFError:
 pass