<wib_jonas> slashlearn ponderthis//Ponder This are monthly open-ended programming puzzle challenges that some regulars enjoy: https://research.ibm.com/haifa/ponderthis/index.shtml

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