def isNum(x):
  return x.isdigit()

input = raw_input().split(' ')
output = set()
right = 'x'
for i in xrange(len(input) - 1, -1, -1):
  if not isNum(input[i]):
    right = 'x'
  elif right == 'x':
    right = input[i]
  elif input[i] != right:
    output.add((input[i], right))

print output