#!/usr/bin/env python

import sys, fileinput

def dropcaps(lines): 
   words = set()
   result = set()

   for line in lines: 
      word = line.rstrip('\r\n')
      capword = word.capitalize()

      words.add(word)
      result.add(word)

      if word != capword: # If the word is lower case
         if capword in words: # If the word was in its upper case form
            result.discard(capword) # Remove the capital case word

      if word == capword: # If the word is capital case
         if word in words: # If the word was in its lower case form         
            result.discard(capword) # Remove the capital case word

   for word in result: 
      print word

def main(): 
   args = sys.argv[1:]
   lines = fileinput.input(args or ['-'])
   dropcaps(lines)

if __name__=="__main__": 
   main()